Nuclear Arms Treaties and Negotiations

Aug. 5, 1963 -- Limited Test Ban Treaty signed in Moscow by the U.S., USSR, and Great Britain; prohibited testing of nuclear weapons in space, above ground, and under water.

Jan. 27, 1967 -- Outer Space Treaty banned the introduction of nuclear weapons and other weapons of mass destruction into space.

July 1, 1968 -- Nuclear Nonproliferation Treaty, with U.S., USSR, and Great Britain as major signers, limited the spread of military nuclear technology by agreement not to assist nonnuclear nations in getting or making nuclear weapons.

May 26, 1972 -- Strategic Arms Limitation Treaty (SALT I) -- interim agreement -- signed in Moscow by U.S. and USSR. The treaty imposed a 5-year freeze on testing and deployment of intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs). An interim short-term agreement putting a ceiling on numbers of offensive nuclear weapons was also signed. SALT I was in effect until Oct. 3, 1977. In the area of defensive nuclear weapons, the separate ABM Treaty limited antiballistic missiles to 2 sites of 100 antiballistic missile launchers in each country (amended in 1974 to one site in each country).

July 3, 1974 -- ABM Treaty Revision (protocol on antiballistic missile systems) and Threshold Test Ban Treaty on limiting underground testing of nuclear weapons to 150 kilotons were signed by U.S. and USSR in Moscow.

Sept. 1977 -- U.S. and USSR agreed to continue to abide by SALT I, despite its expiration date.

June 18, 1979 -- SALT II, signed in Vienna by the U.S. and USSR, constrained offensive nuclear weapons, limiting each side to 2,400 missile launchers and heavy bombers with that ceiling to apply until Jan. 1, 1985. The treaty also set a subceiling of 1,320 ICBMs and SLBMs with multiple warheads on each side. Although approved by the U.S. Senate Foreign Relations Committee, the treaty never reached the Senate floor for ratification because Pres. Jimmy Carter withdrew his support for the treaty following the Dec. 1979 invasion of Afghanistan by Soviet troops.

Dec. 8, 1987 -- Intermediate-Range Nuclear Forces (INF) Treaty signed in Washington, D.C., by USSR leader Mikhail Gorbachev and U.S. Pres. Ronald Reagan, eliminating all medium- and shorter-range nuclear missiles from Europe; ratified with conditions by U.S. Senate on May 27, 1988.

July 31, 1991 -- Strategic Arms Reduction Treaty (START I) signed in Moscow by Soviet Pres. Mikhail Gorbachev and U.S. Pres. George Bush to reduce strategic offensive arms by approximately 30 percent in three phases over seven years. START I was the first treaty to mandate reductions by the superpowers. The treaty was approved by the U.S. Senate Oct. 1, 1992. With the breakup of the Soviet Union in December 1991, four former Soviet republics became independent nations with strategic nuclear weapons on their territory -- Russia, Ukraine, Kazakhstan, and Belarus. The last 3 agreed in principle in 1992 to transfer their nuclear weapons to Russia and ratify START I. The Russian Supreme Soviet voted to ratify Nov. 4, 1992, but Russia decided not to provide the instruments of ratification until Ukraine, Kazakhstan, and Belarus each ratified START I and acceded to the Nuclear Nonproliferation Treaty (NPT) as nonnuclear nations. By late 1993, Belarus and Kazakhstan had ratified START I and acceded to the nonproliferation treaty. In February 1994, Ukraine ratified START II, but it had not yet acceded to the NPT.

Jan. 3, 1993 -- START II signed in Moscow by U.S. Pres. George Bush and Russian Pres. Boris Yeltsin. Potentially the broadest disarmament pact in history, it called for both sides to reduce their long-range nuclear arsenals to about one-third of their then-current levels within a decade and would entirely eliminate land-based multiple-warhead missiles. Action will not be taken on START II until START I enters into force. START II will require ratification only by the U.S. Senate and the legislature of Russia, which would, under the guidelines for START I finalization, be the only remaining nuclear republic of the former Soviet Union