- Signed: 26 May 1972
- Entered into Force: 3 October 1972
- Duration: Five years, unless replaced earlier by an agreement on more complete measures limiting strategic offensive arms.
- Parties: Soviet Union and United States
The earliest efforts to halt the growth in strategic arms launched on a multilateral level and using comprehensive schemes ended in failure. In January 1964, at the Geneva-based Eighteen-Nation Disarmament Committee (ENDC), the United States proposed a verified freeze on the number and characteristics of the US and Soviet strategic nuclear offensive and defensive vehicles, which would be negotiated on a bilateral level. The Soviet Union did not accept this proposal due to the US superiority in the number of weapons at that time. When in 1966 and 1967 the United States proposed that both sides forgo deployment of anti-ballistic missile (ABM) defenses, the Soviet Union offered to include strategic offensive weapons in the discussion of strategic defensive weapons. This proposal was accepted by the United States, and on 1 July 1968, at the signing of the Nuclear Non-Proliferation Treaty (NPT), President Johnson announced that the United States and the USSR had reached an agreement to negotiate limitations and reductions of both strategic offensive and defensive systems.
For some time, due to external and internal reasons, the sides were not able to begin substantive discussions on the subject. Finally, on 20 January 1969, the Soviet Union expressed its willingness to discuss strategic arms limitations. On 17 November 1969, the United States and the Soviet Union began the Strategic Arms Limitation Talks (SALT I) on limiting both ABM defensive systems and strategic nuclear offensive systems. The first real exploration of possible packages began in the spring of 1970. At one point, the sides reached an impasse because of a disagreement on what types of strategic weapons should be included in the treaty. The USSR insisted that the US forward based systems (FBS) were counted in the strategic equation, while the United States believed that FBS and the relevant Soviet short-medium-and intermediate-range strategic systems should be dealt with in a different forum. The second deadlock was caused by disagreement on the scope of the future treaty: the Soviet Union proposed that the negotiations should be limited to discussions of ABM systems only, while the United States insisted that it was essential to make at least a beginning at limiting offensive systems as well. On 20 May 1971, the impasse was broken, when the United States and USSR announced that they had reached a preliminary agreement on a partial constraint on certain strategic offensive systems and on a treaty to limit ABM systems.
After three years of negotiations, during a summit meeting between Nixon and Brezhnev, on 26 May 1972, the talks were concluded with the signing of two basic SALT I documents:
- an Interim Agreement on certain measures limiting strategic offensive arms; and
- the ABM Treaty on the limitation of strategic defensive systems.
It was the first agreement between the United States and the USSR that placed limits and restraints on their nuclear weapons systems.
The Parties undertook not to start construction of additional fixed land-based intercontinental ballistic missile (ICBM) launchers after 1 July 1972 (Article I); Agreed Statement A specified that fixed land-based ABM launchers under active construction as of the date of signature of the Agreement might be completed. The Agreement obligated the Parties not to convert land-based launchers of older types or light ICBMs into land-based launchers for heavy ICBMs of types deployed after 1964 (Article II). The Agreement also limited the numbers of submarine-launched ballistic missile (SLBM) and modern ballistic missile submarines to those operational and under construction on the date of signature of the Agreement (Article III).
The Protocol to the Agreement with regard to Article III, entitled the United States to have no more than 710 SLBM launchers on 44 modern ballistic missile submarines, and the USSR, no more than 950 SLBM launchers on 62 submarines. Additional SLBM launchers in excess of the initial level of 656 for the United States and 740 for the USSR up to the above-agreed levels may become operational as replacements for equal numbers of ICBM launchers of old types deployed prior to 1964 or of SLBM launchers on older submarines.
Subject to the provisions of the Agreement, the Parties received the right to conduct modernization and replacement of strategic offensive ballistic missiles and launchers covered by the Agreement (Article IV). In Agreed Statement C, the Parties expressed understanding that in the process of modernization and replacement, the dimensions of land-based ICBM silo launchers would not be significantly increased. The Parties further expressed a common understanding that the term "significantly increased" means that an increase would not be greater than 10-15 percent of the present dimensions of land-based ICBM silo launchers. The Parties also agreed that there would be no significant increase in the number of ICBM and SLBM test and training launchers, and that construction or conversion of ICBM launchers at test ranges would be undertaken only for purposes of testing and training (Agreed Statement D).
To promote the objectives and implementation of the Agreement, the Parties shall use the Standing Consultative Commission (SCC) established under the 1972 ABM Treaty (Article VI). The Agreement obligated the Parties to continue active negotiations for limitations on strategic offensive arms, whose scope or terms would not be prejudiced by the obligations provided for in this Interim Agreement (Article VII). The Parties agreed that they would observe the obligations of the Agreement and would not take any action prohibited by the Agreement, as well as the ABM Treaty, pending their ratification or acceptance.
Verification and Compliance
The Agreement entitled the Parties to use their national technical means (NTM) of verification to ensure compliance with the Agreement and obligated them not to interfere with NTM of the other Party, nor to use deliberate concealment measures that may impede verification by NTM (Article V).
No mechanisms existed to deal with non-compliance.
The Agreement entitled the Parties to withdraw from the Agreement with a six-month advanced notice if they decide that extraordinary events related to the subject matter of the Agreement have jeopardized their supreme interests. In its Unilateral Statement A, the United States noted that if an agreement providing for more complete strategic offensive arms limitations was not achieved within five years, the US supreme interests could be jeopardized and it would constitute a basis for withdrawal from the ABM Treaty.
In its Unilateral Statement B, the United States stated that it would consider the deployment of operational land-mobile ICBM launchers during the period of the effectiveness of the Agreement as inconsistent with the objectives of the Agreement. The Soviet Unilateral Statement stressed that should NATO allies of the United States increase the number of their modern submarines to exceed the number of submarines they would have operational or under construction on the date of signature of the Agreement, the USSR would have the right to a similar increase in the number of its submarines. In response to this Statement, the United States declared that it did not accept its validity.
The Agreement did not require the Senate's consent for ratification and it entered into force upon exchange of written notices of acceptance by the Parties at the same time as the exchange of instruments of ratification of the ABM Treaty took place, i.e., on 3 October 1972. On 30 September 1972, both houses of the US Senate passed a Congressional Joint Resolution, which urged and requested the President to seek a future treaty that would not limit the United States to levels of intercontinental strategic forces inferior to the limits provided for the USSR. The Agreement was designated "interim" because the Parties intended to continue negotiations. In Article VII of the Agreement, the Parties pledged to continue active negotiations for further limitations on strategic offensive arms. Therefore, in November 1972, the Parties began SALT II negotiations. The Agreement was to expire on 3 October 1977. However, on 23 September 1977, the United States made a unilateral announcement that it would continue to honor the Agreement while SALT II was still being negotiated, provided the USSR would do the same. On 25 September 1977, the USSR made a similar announcement.
SALT refers to two rounds of talks between the US and the USSR on nuclear arms control. SALT I (1969-1972) led to the ABM Treaty.