During Aspin's term the U.S. was concerned that Communist North Korea might have underway a nuclear weapons development program. This gave way to alarm when that country refused to allow full inspection of nuclear sites. In November 1993 North Korea demanded that the United States and South Korea cancel a planned joint training exercise as a precondition during discussions on the nuclear issue. Aspin rejected this demand and announced that the United States would suspend plans to withdraw its troops gradually from the peninsula.