243. Telegram from the Department of State to the Embassy in the Soviet Union1

321521. Geneva for CTB Delegation. Subject: TTBT Data Exchange. Ref: State 315631 (Notal).

1. S—Entire text.

2. In his meeting with Ambassador Dobrynin on December 6,2 the Secretary handed over the following Non-Paper relating to TTBT data exchange noting that this was not just a technical question but a matter of political significance.

Begin text:

Both our governments have recently reaffirmed their intention not to take any actions incompatible with the 150 kiloton limit on underground nuclear explosions called for by the Threshold Test Ban Treaty of 19743 and the Peaceful Nuclear Explosions Treaty of 1976.4 It is in our [Page 595] mutual interest to take steps to minimize any misperceptions regarding adherence to these statements of intent.

The achievement of a CTB retains its very high priority in the view of the USG. It is our desire to move ahead with it expeditiously and to build the popular support needed for its ratification. However, it should be clear that unless we can resolve the current uncertainties regarding nuclear testing, we will be unable to generate and maintain this necessary public support.

[12 lines not declassified]

The Soviet démarche of September 17,5 which raised the question of whether our September 6 event had exceeded 150 kt demonstrates that we indeed have a common problem. We have confirmed that the yield of that US test did not, in fact, exceed 150 kt. However, our own teleseismic measurements suggest that the signals generated, unless analyzed in conjunction with accurate geological and geophysical knowledge of the testing area, could lead to an erroneously high estimate of the yield.

To reduce our uncertainties regarding seismic signals from the Soviet tests I mentioned, we would like to receive from you pertinent geophysical data on the area where these tests were conducted. We would, for our part, be happy to provide to you similar data to reduce the uncertainties you expressed over our test of September 6.

We note that in response to an earlier request which we made for such data, the Soviet side suggested that such uncertainties would not arise if the US had ratified the TTBT. We do not consider this a feasible course of action at this time, as pressing for ratification of the TTBT would complicate our efforts to conclude a CTB—which remains our priority objective in this area. But, as I said, this climate of uncertainty regarding current testing activities undermines the basic political support which a CTB will require.

To make this data exchange as constructive as possible, to reduce the uncertainties which I have described, and to enhance the mutual sense of confidence which is so important in this area, we propose the establishment of an ad hoc joint technical panel or working group.

We would ask this ad hoc panel or group to develop procedures for the exchange of geological and geophysical data for those regions of active test sites where unusual geology and other factors have apparently contributed to incorrect yield estimates that resulted in expressions of concern by both our governments. The concerns we both hold [Page 596] could perhaps be dealt with by precise data on quite limited areas, building on the hypothetical sample profile of a testing area already exchanged in connection with the TTBT. The panel could also develop procedures for participation of US and Soviet experts in an exchange of calibration data from past explosions at these sites. And there are undoubtedly other measures that the panel could consider as well to eliminate unnecessary uncertainties.

End text.

  1. Source: National Archives, RG 59, Central Foreign Policy File, No reel number available. Secret; Immediate. Sent immediate to London and the Mission in Geneva.
  2. Not found.
  3. See footnote 4, Document 141.
  4. See footnote 5, Document 141.
  5. Bessmertnykh delivered the Soviet démarche, which was a reply to the August 24 U.S. démarche, on September 17. The text is in telegram 244481 to Moscow, September 18, (National Archives, RG 59, Central Foreign Policy File, D790425–0762)