The stated rationale was to permit an orderly transition on the part of the nuclear arsenal and its supporting industrial establishment to a permanent no-testing environment.
Importantly, when such a permanent prohibition on testing - in the form of the Comprehensive Test Ban Treaty (CTBT) - was submitted to the U.S. Senate for its advice and consent in 1999, the same considerations that underpinned President Reagan's position on testing were among those that caused a majority of Senators to reject the CTBT.