Mikhail Gorbachev said the Soviet Union has held a ban on nuclear weapons testing for the past year, the first time a Soviet leader has publicly acknowledged the moratorium, an international anti-nuclear group reported Saturday.

The Soviet president, who last week received the 1990 Nobel Peace Prize, expressed his "alarm" over continued nuclear testing and pledged to take up the issue with President Bush when the two next meet, said a spokesman for International Physicians for the Prevention of Nuclear War.The Cambridge-based group, which won the Nobel Peace Prize in 1985, said it received a telegram from Gorbachev stating the Soviet Union has not engaged in nuclear weapons testing during the past year.

"You know the position of the Soviet Union and you are right in saying that the principal strategy of the U.S.S.R in this matter has been actions that would lead to a complete end of nuclear testing," Gorbachev said in a message delivered through the Soviet Embassy in Washington.

"We have proved that those were indeed actions, and not words, by our unilateral moratorium on nuclear weapon tests, which, for reasons beyond our control, did not develop into a complete and definitive cessation of such tests, and by our practices over the past year when we have not conducted a single nuclear test," he said.

Although U.S. officials were aware that the Soviets had not tested nuclear weapons for the past year, this is the first public acknowledgment from Soviet officials, said Peter Zheutlin, director of public affairs for the group.

"Everyone has known it was the case. The important thing is that this is the first public acknowledgment that there is in fact a moratorium," Zheutlin said.

"The significance of this is that nuclear weapons testing is critical in order to modernize a nuclear arsenal. The fact that the Soviets haven't tested in a year means that their nuclear weapons (buildup) is virtually at a standstill," he said.

Zheutlin said Gorbachev had announced a moratorium on nuclear weapons testing in 1985 and invited the United States to reciprocate. The Soviet leader extended his ban through February 1987, but abandoned it when the United States failed to take similar action.