U.S. and Soviet leaders met at the 1955 Geneva Summit, the first such summit since the 1945 Potsdam Conference. No progress was made on major issues; the two sides had major differences on German policy, and the Soviets dismissed Eisenhower's "Open Skies" proposal. Despite the lack of agreement on substantive issues, the conference marked the start of a minor thaw in Cold War relations. Kruschev toured the United States in 1959, and he and Eisenhower conducted high-level talks regarding nuclear disarmament and the status of Berlin. Eisenhower wanted limits on nuclear weapons testing and on-site inspections of nuclear weapons, while Kruschev initially sought the total elimination of nuclear arsenals. Both wanted to limit total military spending and prevent nuclear proliferation, but Cold War tensions made negotiations difficult. Towards the end of his second term, Eisenhower was determined to reach a nuclear test ban treaty as part of an overall move towards détente with the Soviet Union. 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.