MOSCOW — Soviet leader Mikhail S. Gorbachev pledged Thursday that the Soviet Union will refrain from testing any nuclear weapons as long as the United States does the same.
Gorbachev said that a unilateral Soviet moratorium on testing, which had been scheduled to expire March 31, will be in force until the next time the United States detonates a nuclear device.
His promise came a day after President Reagan refused again to accept the Soviet proposal for a mutual test ban as the first step in a wide-ranging disarmament agreement.
In Washington, White House spokesman Larry Speakes said the U.S. position on nuclear testing has not changed.
"Nuclear weapons remain for the foreseeable future an important element of our deterrent force," he said. "The Soviets have made rapid gains in the balance of that, and it is necessary for us and our allies to conduct tests in the near future."
Speakes stressed U.S. demands for "on-site measurement" of nuclear tests.
Gorbachev put the moratorium in effect last Aug. 6, the 40th anniversary of the atomic bombing of Hiroshima, and said it would expire on Dec. 31 unless the United States went along with it. On Jan. 15, the Kremlin extended it to March 31.
Since then, Gorbachev's aides have been encouraged by a resolution favoring a test ban that was passed by the House of Representatives in Washington, matching an earlier endorsement by the Senate. The Reagan Administration opposed the House action.
Gorbachev's latest statement, contained in a letter to heads of six nonaligned nations, apparently was intended to continue pressure on the U.S. Administration to agree to the moratorium.
"Having refrained from all nuclear explosions . . . for over seven months now, we have paid a certain price as it is--both militarily and economically," Gorbachev wrote to leaders of Argentina, Greece, India, Mexico, Sweden and Tanzania.
The six had urged Gorbachev and Reagan not to conduct any nuclear tests until their second summit meeting, scheduled this year in the United States.
Time Running Out
Gorbachev said time was running out for the Reagan Administration to consider the Soviet plan.