- Opened for Signature: 24 September 1996
- Duration: Indefinite
- Depository: UN Secretary-General
Number of Signatories: 183
of the 44 States noted in (Article XIV) Annex 2: 41
Number of Ratifications: 164
of the 44 States noted in (Article XIV) Annex 2: 36
The Comprehensive Nuclear Test Ban Treaty (CTBT) itself includes a Protocol in three parts: Part I detailing the International Monitoring System (IMS); Part II on On-Site Inspections (OSI); and Part III on Confidence-Building Measures (CBMs). There are also two Annexes to the Protocol: Annex 1 detailing the location of various Treaty monitoring assets associated with the IMS; and Annex 2 detailing the parameters for screening events.
The CTBT bans any nuclear weapon test explosion or any other nuclear explosion (i.e., true zero yield).
The CTBT is frequently associated with another key element in the process of nuclear disarmament: a ban on the production of fissile material for anything other than verified peaceful use. Such a ban would impose a quantitative limit on the amount of nuclear material available for weapons use. That objective is the basis for an initiative at the Conference on Disarmament (CD) to negotiate a treaty banning further production of fissile material for weapons purposes — the draft Fissile Material Cut-Off Treaty (FMCT). Taken together, the CTBT and the FMCT are integral components of the nuclear control regime and provide the foundation for eventual nuclear disarmament.
The Treaty establishes a CTBT Organization (CTBTO), located in Vienna, to ensure the implementation of its provisions, including those provisions for international verification measures.
Verification and Compliance
The Treaty's verification regime includes the International Monitoring System (IMS) composed of seismological, radionuclide (16 laboratories), hydroacoustic and infrasound monitoring; consultation and clarification; on-site inspections; and confidence-building measures. When fully operational, the IMS will consist of 321 monitoring stations alongside the existing 16 radionuclide laboratories. The use of national technical means, vital for the Treaty's verification regime, is explicitly provided for. Requests for on-site inspections must be approved by at least 30 affirmative votes of members of the Treaty's 51-member Executive Council. The Executive Council must act within 96 hours of receiving a request for an inspection.
The Treaty provides for measures to redress a violation of the Treaty and to ensure compliance, including sanctions, and for settlement of disputes. If the Conference or Executive Council determines that a case is of particular gravity, it can bring the issue to the attention of the United Nations (Article V of Treaty).
Any State Party to the Treaty may propose an amendment to the Treaty, the Protocol, or the Annexes to the Protocol. Amendments shall be considered by an Amendment Conference and shall be adopted by a positive vote of a majority of the States Parties if no State Party casts a negative vote.
Each State Party has the right to withdraw from the CTBT if it decides that extraordinary events related to the subject matter of the Treaty have jeopardized the State Party's supreme national interests.
Entry into Force
The Treaty will enter into force 180 days after the date of deposit of the instruments of ratification by all States listed in Annex 2 to the Treaty, but no earlier than two years after its opening for signature. Annex 2 lists the following 44 States, Algeria, Argentina, Australia, Austria, Bangladesh, Belgium, Brazil, Bulgaria, Canada, Chile, China, Colombia, Democratic People's Republic of Korea, Democratic Republic of the Congo, Egypt, Finland, France, Germany, Hungary, India, Indonesia, Islamic Republic of Iran, Israel, Italy, Japan, Mexico, Netherlands, Norway, Pakistan, Peru, Poland, Republic of Korea, Romania, Russian Federation, Slovakia, South Africa, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, United States of America, and Vietnam. The aforementioned States are members of the Conference on Disarmament (CD) with nuclear power and/or research reactors. If the Treaty has not entered into force three years after the date of its opening for signature, a conference of the States that have already deposited their instruments of ratification may convene annually to consider and decide by consensus what measures, consistent with international law, may be undertaken to accelerate the ratification process in order to facilitate the early entry into force of this Treaty.
Of the 44 States included in Annex 2 required for entry into force of the CTBT, all have signed with the exceptions of the Democratic People's Republic of Korea (DPRK), India, and Pakistan. Five of the 44 Annex 2 States have signed but not ratified the CTBT; they are China, Egypt, Iran, Israel, and the United States. The United States and China are the only remaining NPT Nuclear Weapon States that have not ratified the CTBT.
Ten years after entry into force, a Conference of the States Parties will be held to review the operation and effectiveness of the Treaty.
Comprehensive Nuclear Test Ban Treaty Organization (CTBTO)
The CTBTO consists of two organs, the Preparatory Commission (a plenary body) and the Provisional Technical Secretariat (PTS).
Provisional Technical Secretariat (PTS)
The PTS began its work on 17 March 1997 and has an international staff of approximately 270 members from 70 countries. The PTS cooperates with the host countries in the development and running of an international network of 321 monitoring stations and 16 radionuclide laboratories.
The main task of the Preparatory Commission is to establish a global verification regime as foreseen in the Treaty so that it will be operational by the time the Treaty enters into force. A worldwide network of 321 monitoring stations and 16 radionuclide laboratories will be built and run by the host countries in cooperation with the Provisional Technical Secretariat. As of January 2011, the CTBTO Preparatory Commission has 79% of the IMS network installed with more than 250 stations are already transmitting data to the International Data Center (IDC) in Vienna via satellite-based global communications infrastructure. Procedures for on-site inspections and CBMs will be developed.
The Preparatory Commission has three subsidiary bodies: Working Group A on administrative and budgetary matters, Working Group B on verification issues, and the Advisory Group on financial, budgetary, and associated administrative issues. Both Working Groups make proposals and recommendations for consideration and adoption by the Preparatory Commission at its plenary sessions. Ambassador Antonio Guerreiro of Brazil is Chairperson of Working Group A, and Dr. Hein Haak of the Netherlands is Chairperson of Working Group B. The Advisory Group, with Michael Weston of the United Kingdom as its Chairperson, is composed of experts of international standing serving in a personal capacity. Ambassador Igor Davidović, Permanent Representative of Bosnia and Herzegovina, is the Chairperson of the Preparatory Commission for 2011.
On 26 February, CTBTO Executive Secretary Lassina Zerbo addressed the Conference on Disarmament in Geneva. Dr. Zerbo stressed the trust and confidence needed to achieve progress in the non-proliferation regime.
From 18 to 19 May, Executive Secretary Zerbo visited Cyprus to attend the International Summit-Conference “Climate Change in the Mediterranean and the Middle East: Challenges and Solutions.” In his keynote speech, Dr. Zerbo addressed the contribution of the CTBTO on climate change.
On 22 May, the Belgian Ministry of Foreign Affairs and the Egmont Institute held a high level meeting on the CTBT with the support of the EU. In his keynote address, Executive Secretary Zerbo acknowledged the “possibility of backsliding into nuclear testing will always remain.”
On April 26, CTBTO Executive Secretary Lassina Zerbo visited Belarus. Dr. Zerbo met with foreign ministers from the Belarusian government to discuss disarmament and the role Belarus as in regional security.
On 2 May, the CTBTO issued a joint appeal with the Japanese foreign minister and the Kazakhstani foreign minister at the 2017 Preparatory Committee for the 2020 NPT Review Conference in Vienna. The appeal emphasized the importance of disarmament in the security of Central and East Asia.
On 3 September, the CTBTO noted unusual seismic activity indicating a sixth nuclear test by the DPRK.
On 20 September, the Conference on Facilitating the Entry into Force of the CTBT was held in New York. Article XIV of the CTBT allows a conference to be held by the majority of ratifying States to examine the requirements for ratification.
From 11 to 14 December, CTBTO Executive Secretary Lassina Zerbo visited France. While there, he and French foreign ministers emphasized France’s commitment to disarmament and the CTBT.
On 7 January, the CTBTO Preparatory Commission held a special meeting after the 2016 DPRK nuclear test. The meeting reviewed the technical findings of the DPRK’s tests. Several Member States urged for the early entry into force of the CTBT.
On 6 June, U.S. Deputy National Security Advisor Ben Rhodes discussed President Obama’s attempts to ratify the CTBT, as well as his attempts to strengthen the norm against nuclear testing.
On 13-14 June, foreign ministers gathered to commemorate the 20th anniversary of the opening for signature of the CTBT. Executive Secretary of the CTBTO Lassina Zerbo urged for the entry into force of the CTBT.
On 24 August, The United States Department of State Spokesperson Mark Toner urged both India and Pakistan to sign and ratify the CTBT.
On 9 September, the CTBTO noted unusual seismic activity indicating a fifth nuclear test undertaken by the DPRK.
On 23 September, the UN Security Council adopted Resolution 2310 (2016) by a vote of 14 in favor and one abstention (Egypt). The resolution urges all States that have yet to sign or ratify the CTBT to do so immediately, and for States to uphold their moratoriums on nuclear weapon tests and nuclear explosions. It also called on all States to support the verification activities of the CTBTO.
On 11 November, CTBTO Executive Secretary Lassina Zerbo paid his first official visit to Cuba. Dr. Zerbo met with Cuban officials to discuss cooperation on science and technology between the CTBTO and the Republic.
On 20 March, Angola became the 164th nation to ratify the CTBT. It signed the treaty on 27 September 1996.
On 29 April, CTBTO Executive-Secretary Dr. Lassina Zerbo delivered a statement to the 2015 NPT Review Conference (27 April – 22 May).
On 4 March, Niue became the 162nd nation to ratify the CTBT. It signed the treaty on 9 April 2012.
On 28 April, the CTBTO Executive Secretary Lassina Zerbo warned the Democratic People’s Republic of Korea to refrain from conducting any further nuclear tests, asserting the strength of the International Monitoring System in detecting these tests.
On 4 September, the Republic of Congo became the 163rd State to ratify the CTBT.
On 3 November, the CTBTO commenced its largest-ever on-site inspection exercise in Jordan. The Integrated Field Exercise (IFE14) included over 200 international experts, 150 tons of equipment, and required 4 years of preparation.
On 9 December, IFE14 concluded. CTBTO Executive Secretary Lassina Zerbo stated the Integrated Field Exercise IFE14 proved it is “absolutely hopeless” to hide a nuclear explosion from the CTBTO.
On 10 January, Brunei Darussalam became the 158th nation to ratify the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Brunei signed the CTBT on 22 January 1997.
On 8 February, Chad became the 159th nation to ratify the CTBT. It signed the treaty on 8 October 1996.
On 24 September, Guinea-Bissau became the 160th nation to ratify the CTBT. It signed the treaty on 11 April 1997.
On 26 September, Iraq became the 161st nation to ratify the CTBT. It signed the treaty on 19 August 2008.
On 12 January, Guatemala became the 156th nation to ratify the CTBT. Guatemala signed the CTBT on 20 September 1999.
On 6 February, Indonesia became the 157th nation to ratify the CTBT after presenting the formal documentation to the United Nations Secretary General in New York. With Indonesia’s ratification complete, thirty-six Annex 2 states have now ratified the CTBT. Currently, eight Annex 2 states must ratify in order for the Treaty to be legally binding.
On 9 April, Niue became the 183rd signatory to the CTBT.
On 19 January, during Chinese President Hu Jintao's official state visit to Washington DC, the United States and China released a joint statement declaring that "both sides support early entry into force of the Comprehensive Nuclear-Test-Ban Treaty (CTBT)" and "agreed to work together to achieve this goal." Neither the United States nor China, Annex 2 states, have ratified the treaty.
On 14 June, Ghana became the 154th nation to ratify the CTBT. Ghana signed the CTBT in October of 1996. All but two countries in Africa have signed the Treaty and all but twelve African countries have now deposited their instruments of ratification.
On 20 September, Guinea ratified the Comprehensive Nuclear Test Ban Treaty and became the 155th State to ratify the Treaty. It signed the CTBT in October of 1996. Currently, only two African countries have yet to sign the CTBT and eleven to ratify it.
On 30 April, Indonesia's Foreign Minister Marty Natalegawa announced that Indonesia would soon ratify the CTBT without waiting for the United States and China to ratify first.
The Central African Republic and Trinidad and Tobago deposited their instruments of ratification on 26 May. These ratifications took place during the last week of the NPT Review Conference. 182 countries have now signed the CTBT and 153 countries have ratified.
On May 4, U.S. President Barack Obama reiterated U.S. commitment to ratifying the CTBT in a statement welcoming Indonesia's announcement of intent to ratify the treaty.
On 8 December, the U.N. General Assembly passed a resolution (A/RES/65/91) calling for an early entry into force of the CTBT in a vote of 179 in favor, 1 against (Democratic People's Republic of Korea), with 3 abstentions (India, Mauritius, and Syria). Like the previous CTBT resolution in 2009, it "stresses the vital importance and urgency of signature and ratification ...in particular those whose ratification is needed for its entry into force, to accelerate their ratification processes with a view to ensuring their earliest successful conclusion."
The resolution welcomed the recent ratifications by Central African Republic, the Marshall Islands and Trinidad and Tobago, as well as recent statements made by certain Annex 2 states regarding their movement towards ratification.
On 2 July 2009, Saint Vincent and the Grenadines became the 181st state to sign the CTBT. With Saint Vincent and the Grenadines' signature, 30 of the 33 States in Latin America and the Caribbean have now signed the Treaty.
On 17 August 2009, Liberia ratified the CTBT, becoming the 149th State to have done so. With this newest ratification, 37 of the 53 African countries have now ratified the Treaty. Approximately two months after signing the CTBT, Saint Vincent and the Grenadines became the 150th State to ratify the Treaty on 23 September 2009. Louis Straker, Deputy Prime Minister and Minister of Foreign Affairs, Commerce and Trade, deposited the instrument of ratification at the United Nations in New York, preceding the commencement of the sixth Conference on Facilitating the Entry Into Force of the CTBT. With this ratification, 29 of the 33 States in Latin America have now ratified the Treaty.
On 8 October, Trinidad and Tobago signed the CTBT, bringing the number of CTBT State Signatories to 182. With the ratification by Trinidad and Tobago, Cuba and Dominica are the only States in Latin American and the Caribbean that have not signed the Treaty.
On 30 October 2009, 175 States voted in favor of the CTBT resolution during the 64th U.N. General Assembly First Committee meeting. Only one country voted against the resolution (North Korea) and three abstained (India, Syria, Mauritius). The backing of the Treaty by nearly every State exemplifies the nearly universal support that the CTBT enjoys. The CTBT resolution was tabled by the original co-sponsors, Australia, Mexico and New Zealand, and was co-sponsored by another 74 States, including for the first time ever, all five permanent members of the Security Council: China, France, Russia, United Kingdom, and the United States.
The resolution "stresses the vital importance and urgency of signature and ratification, without delay and without conditions, to achieve the earliest entry into force of the Comprehensive Nuclear-Test-Ban Treaty... and in particular those whose ratification is needed for its entry into force, to accelerate their ratification processes with a view to ensuring their earliest successful conclusion."
The resolution also welcomed "the ratification of the Treaty by Lebanon, Liberia, Malawi, Mozambique and Saint Vincent and the Grenadines, as well as the signature by Trinidad and Tobago, as significant steps towards the early entry into force of the Treaty."
On 28 October 2009, the Marshall Islands became the 151st State to ratify the CTBT.
On 14 January 2008, Barbados signed and ratified the CTBT. This was followed on 17 January with ratification by Malaysia, which had signed the Treaty in July 1998. Malaysia is the sixth out of the 10 ASEAN countries to ratify the Treaty; it is coordinating CTBT-related issues for the Non-Aligned Movement from 2006-2009 and is active in nonproliferation and disarmament issues.
Colombia became the 35th Annex 2 State to ratify the CTBT on 29 January 2008; Colombia had signed the Treaty on 24 September 1996. After this ratification, nine Annex 2 States must still ratify the Treaty before it can enter into force; the nine States are China, the DPRK, Egypt, India, Indonesia, Israel, Iran, Pakistan, and the United States. At the time, 178 States had signed the CTBT, while 144 States had deposited their instruments of ratification with the United Nations Secretary-General.
On 19 August 2008, Iraq became the 179th state to sign the CTBT. Iraq was one of the few remaining larger countries in the world that had not signed the treaty, and Iraq's signature now brings the total number of signatory states in the critical Middle East and South Asia group to 21 out of 26.
Shortly after a joint ministerial meeting in September 2008, Burundi ratified the Treaty, and Timor Leste signed, bringing the number of signatories to 180 and the number of ratifying states to 145.
Mozambique ratified the treaty on 4 November, and both Malawi and Lebanon deposited their instruments of ratification on 21 November, bringing the number of ratifying states to 148.
The Republic of Moldova deposited its instruments of ratification to the United Nations Secretary-General on 16 January 2007, bringing the total number of ratifications to 138. Moldova's ratification is of particular significance as it completes the ratification of the Treaty by all States in Europe.
The Dominican Republic ratified the Treaty on 4 September 2007, just two weeks prior to the fifth Conference on Facilitating the Entry into Force of the Comprehensive Nuclear-Test-Ban Treaty (Article XIV Conference). The decision by the Dominican Republic followed the ratification of the Treaty by the Republic of Palau on 1 August 2007.
During the first three months of 2006, five States deposited their instruments of ratification with the United Nations. These States are Antigua and Barbuda, Cameron, Suriname, Zambia, and Cape Verde.
On 10 March 2006, Vietnam deposited its instrument of ratification with the United Nations Secretary-General, thus becoming the 34th Annex 2 State to ratify the Treaty. There are now 10 Annex 2 States yet to ratify the treaty before it enters into force.
After declaring its independence on 3 June 2006, and becoming the 192nd member of the United Nations on 28 June 2006, the Republic of Montenegro succeeded to the CTBT on 23 October 2006. Bosnia and Herzegovina deposited its instrument of ratification with the United Nations on 26 October 2006.
Between July and August 2006, three States from three separate CTBT geographical regions deposited their instruments of ratification with the United Nations: Armenia and Andorra both ratified the Treaty on 12 July 2006, while Ethiopia ratified on 8 August 2006.
Convened from 27-30 June 2005, the 24th session of the Preparatory Commission welcomed ratifications by Rwanda and Saint Kitts and Nevis.
Member States welcomed the ratification of the Treaty by the Cook Islands, Djibouti, Madagascar, and Vanuatu during the 25th session of the Preparatory Commission, held from 14-18 November 2005.
The 22nd session of the Preparatory Commission was held from 22-24 June 2004. During the session, Member States welcomed ratifications by Bahrain, Belize, the Libyan Arab Jamahiriya, Serbia and Montenegro, Seychelles, and Sudan. The Commission also determined that Timor Leste would be included in the South East Asia, Pacific and the Far East geo-graphical region.
On 28 September, the Democratic Republic of the Congo deposited its instrument of ratification with the United Nations Secretary-General, thus becoming the 33rd Annex II State to ratify the CTBT. The United Republic of Tanzania signed and ratified the Treaty on 30 September 2004. These ratifications bring the total number of ratifications in the African geographical region to 25, and the total number worldwide to 118.
The 23rd session of the Preparatory Commission, convened from 15-19 November 2004, welcomed the ratifications of the Treaty by the Democratic Republic of the Congo, Liechtenstein, Togo, Tunisia, and the United Republic of Tanzania.
The 20th session of the Preparatory Commission was held from 24-27 June 2003. States Signatories welcomed the signature of the CTBT by Gambia and ratification by Albania, Cote d'Ivoire, Kuwait, Mauritania and Oman, as well as the completion of the national ratification procedure in the Libyan Arab Jamahiriya since the previous session of the Commission.
The 21st session of the Preparatory Commission was held 10-14 November 2003. States Signatories welcomed recent ratifications by Afghanistan, Algeria, Cyprus, Eritrea, Honduras, Kuwait, Kyrgyzstan, and Oman. As of 19 November 2003, the Treaty had been signed by 170 States and ratified by 108. Thirty-two Annex 2 States had already deposited their instruments of ratification with the United Nations Secretary-General.
At the 18th session of the Preparatory Commission, held from 19-22 August 2002, Member States welcomed the ratification of the CTBT by Burkina Faso, Kazakhstan, and Venezuela. Niger ratified the Treaty on 9 September, and Georgia and Samoa ratified on 27 September. Botswana deposited its instrument of ratification with the United Nations Secretary-General on 28 October 2002.
The 14th and 15th sessions of the Preparatory Commission, held from 24-27 April and 21-24 August 2001 respectively, welcomed ratifications by 12 States: Benin, Croatia, Guyana, the Holy See, Kenya, Malta, Namibia, Nicaragua, the Philippines, Saint Lucia, Uganda, and Ukraine.
During the 16th session of the Preparatory Commission, convened from 19-23 November 2001, Member States welcomed the recent ratifications by Costa Rica, Ecuador, Jamaica, Latvia, Nauru, Nigeria, Pa-raguay, Singapore, Sierra Leone, and Uruguay.
At the 12th session of the Preparatory Commission, held from 22-24 August 2000, Member States welcomed ratifications by Chile, Iceland, Portugal, and Russia.
Held in Vienna from 20-21 November 2000, the 13th session of the Preparatory Commission welcomed ratifications by Belarus, Cambodia, Gabon, Kiribati, the Lao People's Democratic Republic, Maldives, and the United Arab Emirates.
The Comprehensive Nuclear-Test-Ban Treaty was adopted by the General Assembly as a resolution (A/RES/50/245) on 10 September 1996. The Treaty opened for signature on 24 September 1996. Between 1996 and 1999 the following States signed and ratified the Treaty: Argentina, Australia, Austria, Azerbaijan, Belgium, Bolivia, Brazil, Bulgaria, Canada, Czech Republic, Denmark, El Salvador, Estonia, Fiji, Finland, France, Germany, Greece, Grenada, Hungary, Ireland, Italy, Japan, Jordan, Lesotho, Luxembourg, Mali, Micronesia (Federated States of), Monaco, Mongolia, Netherlands, New Zealand, Norway, Panama, Peru, Poland, Qatar, Republic of Korea, Senegal, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Tajikistan, Turkmenistan, United Kingdom of Great Britain and Northern Ireland, and Uzbekistan.
The following States signed the Treaty between 1996 and 1999, but had not yet ratified it: Angola, Brunei Darussalam, Burundi, Chad, China, Comoros, Congo, Egypt, Equatorial Guinea, Ghana, Guatemala, Guinea, Guinea-Bissau, Indonesia, Iran (Islamic Republic of), Israel, Liberia, Malawi, Marshall Islands, Mozambique, Myanmar, Nepal, Papua New Guinea, Sao Tome and Principe, Solomon Islands, Sri Lanka, Swaziland, Thailand, United States of America, Yemen, and Zimbabwe.
Point of Contact
Executive Secretary: Lassina Zerbo
Preparatory Commission for the CTBTO
Provisional Technical Secretariat
Vienna International Center
P.O. Box 1200, A-1400 Vienna
Tel: (431) 26030 6200
FAX: (431) 26030 5877
The CTBT prohibits nuclear weapon test explosions. It has not yet entered into force, since three of the 44 required states have yet to sign it and five to ratify it.