Foreign Relations of the United States, 1961–1963, Volumes VII, VIII, IX, Arms Control; National Security Policy; Foreign Economic Policy, Microfiche Supplement

189. Message from Macmillan to President Kennedy, June 22¹

June 22, 1963

Message begins

Thank you for your message about the further suspicious in the Semipalatinsk area. Our experts will not be able to complete their examination of the evidence till Monday, but we must clearly reckon with the possibility that the Russians may be conducting a series of low-yield atmospheric tests.

As you say, our hand may be forced by leaks. I doubt whether the Soviet Government will make a statement. I think it is unlikely that anything will slip out here and I trust you may be able to control what gets out with you, although I know the difficulties. If we fail to control the leaks we may then have to make a statement in advance of the Harriman-Hailsham mission. If so, I regard it as very important that it should be in the nature of a reaction to whatever leak there is, and should keep the temperature down. We might for example say that “signals had been registered consistent with the possibility of low-yield atmospheric tests. This possibility only increased the importance of a test ban agreement and of the Harriman-Hailsham talks.”

I hope however that we can avoid even such a mild statement so near the Moscow meeting.

I am also not sure of the wisdom of a special private message to Khrushchev, in advance of the talks. If, as I sense, he is wavering it might push him in the wrong direction. If, however, we regard the evidence for low-yield atmospheric tests as absolutely certain, I would not object to a message telling Khrushchev that we know of these tests, that we are for the time being keeping our information to ourselves, and that we regard it as important that, until the talks in Moscow have taken place, neither side should conduct any tests in any environment. If we are to do this, I think that we must be very sure indeed of our grounds.

Another possibility, which I am inclined to favour, would be for Harriman and Hailsham to bring up the subject themselves not necessarily at the beginning of their discussions but at a suitable later point. They would of course make it clear that a comprehensive or partial ban would have to cover low-yield atmospheric tests, and, if negotiations looked like resulting in an agreement on the present line, it would be as well for the Russians to know that we have picked up records of events that could be suspected of being small atmospheric explosions. If on the other hand there does not seem any chance of a full-scale agreement, which I would much deplore, and we have to concentrate on a partial arrangement it is just possible that we could try to bargain a limited moratorium on underground tests against a similar moratorium on minor atmospheric tests below a certain threshold. But this needs more thought and discussion before we get into such a complicated field.

It seems to me that the important thing now is to hold the position until the negotiation begins.

1. Provides comments on possible Soviet testing, damage control if suspicious events leaked, wisdom of a private message to Khrushchev, and Hailsham–Harriman mission. Top Secret. 3 p. Kennedy Library, National Security Files, Departments and Agencies Series, ACDA, Test Ban Correspondence, 3/63–6/63.