A U.S. delegation headed by Undersecretary of Commerce Lionel H. Olmer arrived here today for the first round of official talks on U.S.-Soviet trade since 1979.

Meetings of the official U.S.-Soviet working group on trade and economic cooperation were suspended five years ago after the Soviet invasion of Afghanistan.

Since then, U.S.-Soviet trade has fallen off from a peak of $4.4 billion in 1979 to $2.9 billion in 1984. The low point was reached in 1980, during the embargo on U.S. grain sales to the Soviet Union, when trade between the two countries equaled $1.9 billion.

The talks between Olmer and Deputy Foreign Trade Minister Vladimir Sushlov are expected to focus on ways to improve "nonstrategic" trade.

Although trade figures have been rising again recently, U.S. manufacturing exports to the Soviet Union are still small -- $400 million -- and some American businessmen have expressed concern that they are being edged out permanently by Western Europe and Japan.

Western European and Japanese imports to the Soviet Union totaled $40 billion in 1983, compared with $2 billion that year from the United States, according to the U.S.-U.S.S.R. Trade and Economic Council, a business-oriented private group.

The Soviets' major complaint has been with political decisions in Washington that have either halted or restricted trade. Those decisions, the Soviets have noted, have made trading with the United States an unreliable business.

The talks this week are not expected to produce any change in rules regulating East-West trade, particularly in areas of technology regarded as strategic by the U.S. government.

During the past month, Soviet officials have directed several messages to the American business community, urging better economic relations. One such message was delivered by Soviet President Konstantin Chernenko in a meeting last month with Armand Hammer, chairman of Occidental Petroleum.

Dwayne Andreas, chairman of the U.S.-U.S.S.R. Trade and Economic Council, was also in Moscow last month and was received by Soviet Premier Nikolai Tikhonov and Mikhail Gorbachev, widely viewed as a leading contender to be Chernenko's eventual successor.

The United States lifted restrictions last week on the sale of personal computers to the Soviet Union while tightening rules against the transfer of more sophisticated computer software.

The rules change came about through agreements reached by the 15-nation coordinating committee on strategic exports known as Cocom that is based in Paris and groups the NATO allies and Japan.

In Washington, the State Department announced that the U.S. Coast Guard and Soviet Merchant Marine opened talks Monday on improving cooperation and communications in search and rescue operations in waters between the Alaskan and Siberian coasts. The talks, at Coast Guard headquarters, are to continue through Wednesday.