The Shifting Dynamics of UK-US Nuclear Weapons Cooperation: From the 1958 Mutual Defense Agreement to Today

UK NUCLEAR DEFENCE POLICY AND WEAPONS PLAN 1987

References:
A. CDS 1140/1 dated 9 June 198?.
B. MO 18/1/1L dated 8 July 198?.

1. When endorsing the 1987 UK Nuclear Defence Policy and Weapons Plan forwarded to the Secretary of State at Reference A, it was noted that the UK was becoming increasingly dependent on the US for certain non-operational aspects of the UK's nuclear program. Subsequently, at Reference B, you requested information on the obligations the US is under to continue providing the UK with assistance and information on nuclear matters, and how easily these obligations could be rejected.
2. All interactions with the US on nuclear matters are governed by the US/UK Agreement for Cooperation on the Uses of Atomic Energy for Mutual Defence Purposes signed in 1958, and which has been extended to run until 1994. The agreement can be terminated by either party with one year’s notice, and either party may request a review after 5 years; any resulting changes, additions, or deletions require formal approval by both governments. Since 1958, there have been extensions to the agreement in the form of annexes, and although these items are not part of a contractual commitment, the US has honored them in full.
3. The continuing exchange of information under the agreement is very much dependent upon a US assessment of UK capability. When the UK ceased nuclear testing between 1963 and 1971, the US withdrew support from all but basic technology matters. Previous exchanges on nuclear design have now been completely restored and extended, commensurate with the UK's strides forward since resuming testing. For example, the successful demonstration by the UK that we could complete the Chevaline warhead on our own, and the demonstration of advanced warhead designs in underground tests, both provided us with the key to unlock the nuclear aspects of the US Trident system.
4. Separate from the 1958 Agreement, the US/UK Polaris Sales Agreement (PSA) was signed in April 1963. It has treaty status and creates continuing rights and obligations under international law; it is not an agreement concerned with nuclear matters.
5. Article III of the PSA obliges the US Government "to provide missiles (less warheads), equipment, and supporting services of such types and in such quantities as the Government of the UK may from time to time require, and in configurations and in accordance with delivery programs or timetables to be agreed between the project officers." Formal joint annual reports of progress made under the PSA are provided to the contracting governments by National Projects Officers. This obligatory mechanism serves as a check that the continuing rights and obligations under the PSA are being met.
6. Agreed minutes and exchanges of notes in connection with the PSA were also issued at the same time. These exchanges explicitly acknowledged the continuing nature of the obligations under the Agreement and also created a linkage between the PSA and the 1958 Agreement. In September 1980, it was agreed that the PSA should also apply to the Trident weapon system.
7. The legal and contractual obligations the US has undertaken in the PSA are as tight as the UK could reasonably expect. The UK has had, and should continue to have, considerable benefits from the operation of the PSA, and these benefits are judged to be appreciably greater than those the UK would have obtained under the Foreign Military Sales regime, which now governs the supply of most US weapons to the UK. Similarly, the terms of the 1958 Agreement are the best the UK could have obtained. However, there can be no guarantee that if, in the view of the US administration, its own interests are being harmed, or the UK’s capabilities and commitments are judged insufficient, the agreement will not be terminated.
8. Finally, I should also add that the US has not been, nor is it likely to be, dependent upon the UK in nuclear matters to any significant extent. Although the UK recently loaned the US a quantity of Tritium because their own production capacity had been reduced, it was an extremely small proportion of the total US need. Similarly, while the UK technical input to the US over the years as part of the 1958 Agreement has been helpful, no single issue could have been used as a bargaining counter.

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