The Treaty on the Limitation of Underground Nuclear Weapon Tests, also known as the Threshold Test Ban Treaty (TTBT), was signed in July 1974. It establishes a nuclear "threshold," by prohibiting tests having a yield exceeding 150 kilotons (equivalent to 150,000 tons of TNT).
Agreement on the Threshold Test Ban Treaty was reached during the summit meeting in Moscow in July 1974. For many years, neither the United States nor the Soviet Union ratified the TTBT or the PNE Treaty. However, in 1976 each party separately announced its intention to observe the Treaty limit of 150 kilotons, pending ratification. Agreement on additional verification provisions, contained in new protocols, substituting for the original protocols, was reached in June 1990. The TTBT and PNET entered into force on December 11, 1990.
Primary documents, including treaty text and associated memoranda, statements and other related material.
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