asked Her Majesty's Government:Whether they have discussed with the United States Administration the period over which that Administration considers itself bound by a strict interpretation of the Anti-Ballistic Missile (ABM) Treaty of 1972, given that one of the Secretary of Defense's Deputies is reported in an official United States Information Service text to have stated that in the long run "there is no rational basis" for the United States to hold to a "restrictive interpretation" of the ABM Treaty that would limit ABM systems, and whether the co-operation extended by them to the United States Administration under the secret Memorandum of Understanding would be affected in any way by a shift of interpretaion from "restrictive" to "permissive".
President Reagan last October reaffirmed that the SDI research programme would continue to be conducted in accordance with a restrictive interpretation of the ABM Treaty's obligations, and the British Government welcomed this decision. The US administration has confirmed that this remains US policy. The US Administration has also made clear that participation by the allies will also be consistent with US treaty obligations. It is for the parties to the ABM Treaty to interpret it, though the implications of any proposed change in US policy would need to be considered carefully by HMG.