Foreign Relations of the United States, 1964–1968, Volume XI, Arms Control and Disarmament

66. Oral Reply From the Soviet Ambassador (Dobrynin) to Secretary of State Rusk¹

Washington, January 25, 1965.

An underground nuclear explosion was indeed carried out in the Soviet Union.² This explosion was carried out deep down underground. The quantity of radioactive debris that leaked into the atmosphere was, however, so insignificant that a possibility of its fallout outside the territorial limits of the Soviet Union should be excluded. Thus, the underground explosion that was carried out does not affect the provisions of the Treaty Banning Nuclear Weapons Tests in the Atmosphere, in Outer Space and Underwater.

1. Source: Johnson Library, National Security File, Subject File, Nuclear Testing—USSR, Vol. I, Box 31. Confidential; Limdis. A copy is also reproduced in Seaborg, Journal, Vol. 10, p. 101.
2. Regarding this Soviet test, see Document 62.