MOSCOW, JAN. 12 -- The Soviet Union said today that it would suspend underground nuclear tests for four months in response to domestic protests.

Deputy Prime Minister Igor Belousov made the announcement to the Supreme Soviet, the standing legislature, a few days after President Mikhail Gorbachev failed to win U.S. support for a total test ban. Belousov said the Kremlin had made the decision in a bid to find "an acceptable solution to the social and economic problems involved in the holding of nuclear tests."

In the last two years, a powerful anti-test movement has emerged in Kazakhstan in Central Asia, where the Soviet army's main testing grounds are located in the Gegelen Hills near the city of Semipalatinsk. Kazakhstan's new president and Communist Party chief, Nursultan Nazarbayev, backed the movement -- and the military switched the testing program last year to the Arctic island of Novaya Zemlya. This sparked protests in Soviet Arctic and from Scandinavian countries.

In 1986 and 1987, the Soviet Union observed a 19-month test freeze as Gorbachev sought to build up his credentials as a peacemaker, but he failed to persuade then-President Ronald Reagan to follow suit.

During the past week, U.S. officials again rejected a similar suggestion from Gorbachev, which he sent to a United Nations conference on nuclear testing. They said tests were essential to keep American weaponry effective.

Soviet military spokesmen have consistently used the same argument. Although formally expressing support for the previous moratorium, senior army officers privately argued it would reduce Moscow's defense capacities.