After nearly a half-century of international efforts to bring about the cessation of nuclear testing, the Comprehensive Nuclear-Test-Ban Treaty (CTBT) opened for signature on 24 September 1996 at the United Nations in New York. On that day, the Treaty was signed by over 70 states, including all five NPT-designated nuclear weapon States (NWS). While addressing the United Nations General Assembly in 1997, then U.S. President Bill Clinton described the CTBT as the "the longest-sought, hardest-fought prize in the history of arms control." However, due to the stringent entry into force provisions of the CTBT which require that 44 so-called "Annex 2 States" sign and ratify the Treaty, thirteen years have passed without a legally binding nuclear test ban coming into force. Annex 2 States are countries that possessed nuclear reactors in 1996 and participated in CTBT negotiations at the Conference on Disarmament from 1993-96. Of these 44 states, 35 have signed and ratified the Treaty, six have signed but not ratified (China, Egypt, Indonesia, Iran, Israel, and the United States), and three have yet to sign (the DPRK, India, and Pakistan).

Unlike the Partial Test Ban Treaty (1963) that banned nuclear testing in the atmosphere, underwater, and outer space, the CTBT prohibits all nuclear explosions in all environments. After the CTBT enters into force, compliance with the Treaty will be monitored by a global verification regime that will search the earth for evidence of a nuclear explosion. In order to meet this objective, the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) was created with the mandate to develop the CTBT's verification regime, as well as promote the Treaty's entry into force. The verification regime is comprised of a global network of monitoring facilities, the International Data Centre (IDC), where CTBTO staff members analyze data from monitoring stations and then distribute this information to member states, and provisions for intrusive on-site inspections in the event of a suspected explosive nuclear test. Upon completion, the IMS will consist of 337 monitoring facilities strategically located throughout the world in nearly 90 countries. As of September 2009, approximately 250 of these facilities had met CTBTO certification specifications and were successfully transmitting monitoring data to the IDC for analysis. Even though the International Monitoring System (IMS) has not yet reached completion, it quickly and accurately identified both nuclear tests conducted by the DPRK in 2006 and 2009.

In order to accelerate the Treaty's entry into force, the CTBTO has convened Conferences on Facilitating the Entry into Force of the Comprehensive Nuclear-Test-Ban Treaty (Article XIV Conferences) biennially since 1999. The sixth Article XIV Conference was held from 24-25 September 2009 at the United Nations in New York, where delegations from more than 100 states gathered to discuss means with which to promote the Treaty's entry into force. The conference commenced thirteen years to the day since President Clinton became the first world leader to sign the CTBT. Although the George W. Bush administration opposed the CTBT, which stalled significant political progress on promoting ratifications by the remaining Annex 2 States, President Obama has voiced his broad support for the Treaty. Furthermore, the Obama administration has committed to "immediately and aggressively" pursuing U.S. ratification and working with the other Annex 2 States and the international community to achieve the Treaty's entry into force. There is an emerging bipartisan consensus in the United States, signified most notably by the Wall Street Journal article by George P. Shultz et al. calling for a world free of nuclear weapons, that the CTBT constitutes a core element of the international nonproliferation regime designed to counter the threats posed by the existence of nuclear weapons.

Underscoring the importance that President Obama has assigned to the CTBT, Secretary of State Hillary Clinton led the U.S. delegation and delivered the U.S. national statement during the 2009 Article XIV Conference. Secretary Clinton's strongly worded speech during the conference sent a clear message that the United States was once again engaged on the issue stating that, "It has been a long time since our government was represented at this conference. We are glad to be back." Delegates at the conference unanimously applauded U.S. participation in the conference and expressed their appreciation for the ambitious arms control agenda laid out by the Obama administration. In a further show of U.S. support for addressing the nuclear threat through multilateral institutions, President Obama chaired a special Security Council summit on nuclear nonproliferation and disarmament that coincided with the first day of the CTBT Conference. The summit was attended by 14 heads of state and succeeded in unanimously adopting a U.S. sponsored resolution outlining a path that the international community would embark on to work towards a world free of nuclear weapons. Significantly, the resolution contained a strong statement calling on states to sign and ratify the CTBT in order to achieve its entry into force at an early date. With this resolution, as well as other statements from President Obama at the United Nations General Assembly and the Security Council Summit, the Obama administration has clearly embraced the test ban as a fundamental component of the international nonproliferation regime, the foundation of which established by the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).

The CTBT was a core element of the package of decisions and resolution on the Middle East that paved the way for the indefinite extension of the NPT in 1995, as well as the 13 practical steps towards nuclear disarmament agreed upon at the 2000 NPT Review Conference. In recent years, the international nonproliferation regime has been under severe duress as the withdrawal of the DPRK from the NPT, Pyongyang's subsequent nuclear tests, the revelations of Iran's secret nuclear weapon activities, and Syria's apparent clandestine nuclear program have called into question the ability of the regime to deal with new nuclear threats. The 2010 NPT Review Conference must adopt tangible measures to strengthen this regime and ensure its continued vitality and legitimacy, and the Obama administration considers making progress on accelerating the entry into force of the CTBT essential to achieving that objective.

The CTBT now boasts over 180 signatories and 150 ratifications, making it one of the most widely subscribed to treaties in history. Furthermore, the UN General Assembly First Committee passed a resolution in 2008 calling for the entry into force of the CTBT with 168 states voting in favor, three abstaining (India, Mauritius, and Syria), and only one state voting against (the United States). Recent events illustrate the increasing political momentum surrounding the Treaty, and an atmosphere of optimism has permeated discussions over the prospects for U.S. ratification and the Treaty's entry into force. Nonetheless, while the political environment has changed in the United States, it is also clear that securing U.S. Senate ratification necessitates serious, sustained efforts from the Obama administration and proponents of the Treaty. Similarly, promoting the Treaty's entry into force will require significant political will from the international community. The 2009 Article XIV Conference in New York served as an important venue for states to voice their continued support for the Treaty, and the conference adopted a consensus Final Declaration and Measures to Promote the Entry into Force of the CTBT. Although U.S. reengagement on the test ban issue, as well as in the international nonproliferation regime, has certainly created an air of optimism, it remains to be seen whether the successful outcome of the conference will provide the necessary political momentum to make progress on the Treaty's entry into force before the 2010 NPT Review Conference.