Soviet Union. The Soviets dismissed the US argument as a ruse, suggesting that the Hardtack data had been falsified. In early 1959, a roadblock to an agreement was removed as Macmillan and Eisenhower, over opposition from the Department of Defense, agreed to consider a test ban separately from broader disarmament endeavors. On 13 April 1959, facing Soviet opposition to on-site detection systems for underground tests, Eisenhower proposed moving from a single, comprehensive test ban to a graduated agreement where atmospheric tests—those up to 50 km (31 mi) high, a limit Eisenhower would revise upward in May 1959—would be banned first, with negotiations on underground and outer-space tests continuing. This proposal was turned down on 23 April 1959 by Khrushchev, calling it a "dishonest deal." On 26 August 1959, the US announced it would extend its year-long testing moratorium to the end of 1959, and would not conduct tests after that point without prior warning. The Soviet Union reaffirmed that it would not conduct tests if the US and UK continued to observe a moratorium. To break the deadlock over verification, Macmillan proposed a compromise in February 1959 whereby each of the original parties would be subject to a set number of on-site inspections each year. In May 1959, Khrushchev and Eisenhower agreed to explore Macmillan's quota proposal, though Eisenhower made further test-ban negotiations conditional on the Soviet Union dropping its Control Commission veto demand and participating in technical discussions on identification of high-altitude nuclear explosions. Khrushchev agreed to the latter and was noncommittal on the former. A working group in Geneva would eventually devise a costly system of 5–6 satellites orbiting at least above the earth, though it could not say with certainty that such a system would be able to determine the origin of a high-altitude test. US negotiators also questioned whether high-altitude tests could evade detection via radiation shielding. Concerning Macmillan's compromise, the Soviet Union privately suggested it would accept a quota of three inspections per year. The US argued that the quota should be set according to scientific necessity (i.e., be set according to the frequency of seismic events). In June 1959, a report of a panel headed by Lloyd Berkner, a physicist, was introduced into discussions by Wadsworth. The report specifically concerned whether the Geneva System could be improved without increasing the number of control posts. Berkner's proposed measures were seen as highly costly and the