The Soviet Union, which has repeatedly protested American restrictions on trade, has informed the United States it will sharply reduce imports of American goods and equipment.

This step backward in U.S.-Soviet trade was disclosed by Secretary of Commerce Juanita M. Kreps yesterday at the end of the Carter administration's first talks under the U.S.-Soviet Commercial Commission established in 1972.

The Soviet delegation, headed by Soviet Trade Minister Nikolai S. Patolichev, Kreps said, stated that Russian imports of American non-agricultural products "will drop sharply this year, and next as well, from a current annual level of about $800 million."

Patolichev, a U.S. source said, told the U.S. delegation that Soviet imports in this category will be cut in half, because of American trade and credit restrictions.

In late 1974, Congress tied that granting of most-favored-nation trade benefits for the Soviet Union to freer emigration of Soviet Jews, in the Jackson-Vanik amendment, and also put tight limits on Export-Import Bank credits for Soviet trade. The Soviet Union, in turn, refused to bring into force a U.S. Soviet Trade Agreement, signed in 1972.

Treasury Secretary W. Michael Blumenthal and Kreps, at a news conference yesterday, treated the new Soviet action as a limited move. Despite the dispute over U.S. trade restrictions, "trade between out two countries in the last two years has reaches record levels," Kreps said.

Blumenthal said the Soviets' "total volume of imports from all sources is being reduced, because they have a pretty severe (trade) imbalance, and some restrictions on foreign exchange availability."

American firms, Blumenthal said, currently are engaged in negotiations for potential trade totaling "up to $6 billion" in silicones, steel plants, aluminum smelter technology and petrochemical projects.

American-Soviet trade is far out of balance in U.S. favor.In 1976, U.S. sales to the Soviet Union totaled $2.3 billion, most of it in grain and other agricultural products, which Kreps noted would be unaffected by the new Soviet decision. The Soviet Union, in 1976, sold only $221 million worth of exports to the United States.

Blumenthal told reporters "we do not at this point have any proposals" for asking Congress to remove the trade-emigration legislation sponsored by Sen. Henry M. Jackson (D-Wash.) and Rep. Charles A. Vanik (D-Ohio), or the restrictions on credits for the SovietUnion.

These restrictions have "to be seen in the overall context of U.S. Soviet relations," he said, and the Soviet delegation was told that the Carter administration hopes they will improve enough "for us to secure some change from the Congress." "Human rights," Blumenthal said, are "an important aspect of the problem."

Kreps said a decision "has not been made" by the Carter administration on an important American computer, the Cyber 76, which the Soviet Union badly wants. According to other sources. President Carter already has decided against that sale, on security grounds.

This computer is described as 15 to 20 times more powerful than any the Soviet Union now possesses. The U.S. concern is that it could be diverted to major military use.