January 13, 1987

To the Senate of the United States:

Two treaties between the United States of America and the Union of Soviet Socialist Republics on (1) the Limitation of Underground Nuclear Weapon Tests, and the Protocol thereto, known as the Threshold Test Ban Treaty (TTBT) signed in Moscow on July 3, 1974, and (2) Underground Nuclear Explosions for Peaceful Purposes, and the Protocol thereto, known as the Peaceful Nuclear Explosions Treaty (PNET) signed in Washington and Moscow on May 28, 1976, were transmitted to the Senate by President Ford on July 29, 1976 with a view to receiving advice and consent to ratification. (Senate Executive N, 94th Cong., 2d Sess.) Although hearings were held a year later, the Senate itself has not acted on the treaties. I ask the Senate to consider these important treaties anew in light of developments that have taken place over the last decade.

On August 14, 1986, I transmitted to the Congress a comprehensive study which stated U.S. national security concerns as well as our views on necessary verification improvements to the TTBT and the PNET, in response to the requirements of Section 1003 of the FY 1986 Department of Defense Authorization Act (P.L. 99 - 145). I am enclosing a copy of this study and commend it to your attention.

The security of the United States and the entire free world, today and for the foreseeable future, depends on the maintenance of an effective and credible nuclear deterrent by the U.S. This is a considerable challenge, in light of continuing efforts by the Soviet Union to undercut the effectiveness of our deterrent. With the support of Congress we have succeeded in meeting this challenge, and together we must continue to do so in the future.

Today I am requesting per my October 10, 1986 letter that the Senate give advice and consent, subject to the condition set out below, to two pending treaties that have significant implications for Western security: the TTBT and PNET. These treaties have the common purpose of limiting individual nuclear explosions to no more than 150 kilotons. The TTBT, which prohibits nuclear weapon tests above 150 kilotons, places significant constraints on the efforts we may undertake in the U.S. nuclear test program to respond to Soviet nuclear and non-nuclear activities aimed at undercutting our deterrent. Hence, it is imperative that we have the necessary provisions that will make the TTBT effectively verifiable and thus assure ourselves that the Soviet Union is fulfilling its obligations and is thereby equally constrained.

Unfortunately, as I have frequently stated and the enclosed study makes clear, the TTBT and PNET are not effectively verifiable in their present form. Large uncertainties are present in the current method employed by the United States to estimate Soviet test yields. I have on several occasions reported to the Congress on the problems with Soviet compliance with the TTBT. Therefore, achieving Soviet agreement to improved verification measures that would provide for effective verification of these treaties has been my highest priority in the area of nuclear testing limitations.

As I stated in my March 14, 1986 letter to General Secretary Gorbachev, effective verification of the TTBT and PNET requires that we reduce the current unacceptable level of uncertainty in our estimates of the yields of nuclear tests. Indeed, leaders in previous Congresses have shared my view that the present large degree of uncertainty in such estimates is unacceptable, as well as my desire for sharp improvements. In this regard, we require -- and have conveyed to the Soviets that we require -- effective verification through direct, on-site hydrodynamic yield (CORRTEX) measurement of all appropriate high-yield nuclear detonations. Further, I informed General Secretary Gorbachev that, if the Soviet Union would agree to essential verification procedures for the TTBT and the PNET, I would then be prepared to request the advice and consent of the Senate to ratification of the treaties. Ratification of the treaties without such provisions would be contrary to the national security interests of the United States.

As written, the TTBT relies solely on teleseismic detection and yield measurement systems and on inadequate, and unverifiable data exchange. The Soviet Union has apparently had problems in correctly assessing the yields of U.S. nuclear tests. Despite our best efforts, the Soviet Union has so far not accepted our practical proposal for achieving the necessary verification improvement of the TTBT and the PNET. We have not yet found any alternative approach which equals the effectiveness of CORRTEX -- we are striving to achieve a yield-estimation accuracy of about 30 percent by this method. We have, nonetheless, advised the Soviets, at three Geneva nuclear testing experts meetings in 1986, that the U.S. is willing to consider any other direct yield measurement method the Soviets might propose, provided it is at least as capable (in terms of accuracy and non-intrusiveness) as CORRTEX. To date, they have not been forthcoming in proposing or explaining alternative verification techniques that would meet our requirements.

Recognizing the role of the Senate in the ratification process, I am therefore requesting that the Senate give its advice and consent to ratification of the TTBT and the PNET, subject to a condition in the following form:

``The Senate's Resolution of advice and consent to ratification is subject to the condition that the President shall not proceed with ratification of the Treaty on Limitation of Underground Weapon Tests and the Treaty on Underground Nuclear Explosions for Peaceful Purposes until the President has certified to the Senate that the Union of Soviet Socialist Republics has concluded with the United States additional agreements expanding upon the obligations stated in Article II of the Treaty on Limitation of Underground Weapon Tests and including provisions for direct, accurate yield measurements taken at the site of all appropriate nuclear detonations so that the limitations and obligations of these treaties, inter alia the 150 kiloton limit, are effectively verifiable, and until such agreements have been submitted to the Senate, and the Senate has advised and consented to their ratification.''

I am hopeful we can reach an agreement with the Soviet Union which will allow me to certify that the treaties are effectively verifiable. I will be prepared to ratify the TTBT and the PNET at such time as the condition cited above has been fulfilled.

Further, I informed the General Secretary in Reykjavik that, once our verification concerns have been satisfied and the treaties have been ratified, and in association with a program to reduce and ultimately eliminate all nuclear weapons, I would propose that the United States and the Soviet Union immediately engage in negotiations on ways to implement a step-by-step parallel program of limiting and ultimately ending nuclear testing.

The steps in this program would take into account our long-standing position that a comprehensive test ban is a long-term objective which must be viewed in the context of a time when we do not need to depend on nuclear deterrence to ensure international security and stability, and when we have achieved broad, deep, and verifiable arms reductions, substantially improved verification capabilities, expanded confidence-building measures, and greater balance in conventional forces.

Ronald Reagan

The White House,

January 13, 1987.