As a counter-offer, the British proposed limiting the British programme in return for American bombs. The opposition of key American officials, including Lewis Strauss from the United States Atomic Energy Commission (AEC), and Senators Bourke B. Hickenlooper and Arthur Vandenberg of the Joint Committee on Atomic Energy (JCAE), coupled with security concerns aroused by the 2 February 1950 arrest of the British physicist Klaus Fuchs as an atomic spy, caused the proposal to be dropped. The June 1951 defection of Donald Maclean, who had served as a British member of the Combined Policy Committee from January 1947 to August 1948, reinforced the Americans' distrust of British security arrangements.