Soviet leader Mikhail Gorbachev announced a unilateral Soviet moratorium on nuclear testing in late July 1985. The ban took effect on Aug. 6, 1985, the 40th anniversary of the US atomic bombing of Hiroshima, Japan, and was to continue until the end of the year. It applied to underground nuclear tests, the only ones allowed under the 1963 Limited Test Ban Treaty. On Jan. 15, he extended the ban through March 31.
Two weeks before it was to expire, he said the moratorium would continue until the next US nuclear test. That test came April 10. Though the Soviet news agency Tass announced the next day that the Kremlin was ending the ban, Mr. Gorbachev extended it to Aug. 6 after the Chernobyl nuclear accident.
On March 29, he called for talks with President Reagan on a test ban, which the US rejected. But US and Soviet delegations met recently in Geneva to discuss issues related to nuclear testing.
The US has conducted 15 underground nuclear tests since the moratorium began. It has given a number of reasons for rejecting a complete test ban. It dismissed the Soviet moratorium as ``a propaganda ploy'' and said the Soviets had accelerated their nuclear testing before the ban. It also said that Soviet compliance could not be verified. And the US said testing was necessary to keep a reliable nuclear stockpile as a deterrent to war and to build a new generation of nuclear weapons.
Perhaps most important, nuclear tests are necessary in the development of Mr. Reagan's Strategic Defense Initiative (``star wars''), a point the Soviets have noted.