Eisenhower's 1952 candidacy was motivated in large part by his opposition to Taft's isolationist views; he did not share Taft's concerns regarding U.S. involvement in collective security and international trade, the latter of which was embodied by the 1947 General Agreement on Tariffs and Trade. Khrushchev had also become increasingly interested in reaching an accord, partly due to the growing Sino-Soviet split. By 1960, the major unresolved issue was on-site inspections, as both sides sought nuclear test bans. Hopes for reaching a nuclear agreement at a May 1960 summit in Paris were derailed by the downing of an American U-2 spy plane over the Soviet Union.The Eisenhower administration, initially thinking the pilot had died in the crash, authorized the release of a cover story claiming that the plane was a 'weather research aircraft' which had unintentionally strayed into Soviet airspace after the pilot had radioed 'difficulties with his oxygen equipment' while flying over Turkey.