The Threshold Test Ban Treaty (TTBN), signed on 3 July 1974 between the United States and the Soviet Union, set limitations on underground nuclear tests. The TTBN followed the 1963 Partial Teat Ban Treaty (PTBT). The TTBN limited the size of any nuclear test by setting a ceiling threshold of 150 kilotons for any underground nuclear test. This limit was designed specifically to prevent both the Soviets and Americans from developing warheads that would allow for a first-strike capability. Treaty terms included provisions for exchange of data and designation of the test sites. Complementing the TTBN was the Peaceful Nuclear Explosions (PNE) Treaty, signed in April 1976.
Critics of the TTBN focused on Soviet violations; the 150 kiloton limit, which many regarded as too high; and the lack of adequate verification procedures. Following agreement on the latter in July 1990, the U.S. Senate ratified both the TTBN and the PNE in December 1990.
Spencer C. Tucker
U.S. Arms Control and Disarmament Agency. Arms Control and Disarmament Agreements: Texts and Histories of the Negotiations. Washington, DC: U.S. Government Printing Office, 1990.