Foreign Relations of the United States, 1969–1976, Volume E–14, Part 2, Documents on Arms Control and Nonproliferation, 1973–1976

196. Memorandum From the President’s Assistant for National Security Affairs (Scowcroft) to Secretary of State Kissinger, Secretary of Defense Rumsfeld, the Director of the Arms Control and Disarmament Agency (Iklé), and the Administrator of the Energy Research and Development Administration (Seamans)¹

Washington, May 27, 1976.

SUBJECT

• Threshold Test Ban Treaty Oral Understanding

The Agency positions and previous negotiating record concerning the Threshold Test Ban Treaty oral understanding on slight unintentional breaches of the threshold have been reviewed. As a result, it has been decided that:

—The U.S. will draw no distinction between “actual” and “design” yield with regard to the type of yield intended in the Treaty.

—The U.S. will conduct nuclear weapons tests in accordance with previous guidance contained in the Under Secretaries Committee report on the second-half FY 76 test program and approved in NSDM 319—i.e., we will test at design yields up to 150 kilotons.

—As required by NSDM 319, the Under Secretaries Committee testing policy should be revised in the next semi-annual nuclear weapons test program review “to include recommended measures to reduce the probability of yields in excess” of the threshold.

In light of his previous discussion with the Soviets pursuant to NSDM 256, Ambassador Stoessel should review with the Soviets the previous understanding and confirm the following points:

—Both sides will make every effort to comply fully with all provisions of the Threshold Test Ban Treaty.

—As agreed in previous discussions, there are technical uncertainties associated with predicting the precise yield of nuclear weapon tests. These uncertainties may result in slight unintended breaches of the 150 kiloton threshold.

—We will testify during ratification hearings that we have discussed this problem with the Soviets and agreed that:

• One or two slight unintended breaches per year would not be considered a violation of the Treaty.

• Such breaches would be cause for concern, however, and, at the request of either party, would be the subject of consultations.

—We will also testify that while we would not consider a slight, unintentional breach a violation, we would carefully review each such breach to ensure that it is not part of a general attempt to exceed the confines of the Treaty.

In the course of this discussion, Ambassador Stoessel should not commit the U.S. to any magnitude of such a breach that might be permissible. He should conclude the discussion by reaffirming that all aspects of this oral understanding will become a matter of public record during our ratification hearings.

Brent Scowcroft

1. Summary: Scowcroft noted that the agency positions and previous negotiating record concerning the TTBT oral understanding on slight unintentional breaches of the threshold had been reviewed. As a result, he stated, the administration had approved three positions regarding the oral understanding.

   Source: Central Intelligence Agency, OP 10 (Executive Registry Subject Files (DCI Area), Job 79M00467A, Box 25, Folder 472, NSC Under Secretaries Committee, 010176–311276. Secret. Copies were sent to Brown and Bush. NSDM 319, “Underground Nuclear Test Program for the Second Half of FY 1976 and the Transition Quarter (1),” March 2, is in the Ford Library, National Security Council, Institutional Files—NSDMs, Box 63, NSDM 319. NSDM 256 is Document 54. For the “oral understanding,” see Document 183.