If the Administration agrees to the talks, "we could probably do it in the spring . . . in April or early May," said Lionel L. Olmer, the Commerce Department's senior foreign trade representative, who plans to brief Cabinet members this week on recent negotiations with the Soviets in Moscow. Olmer and 10 colleagues met for more than two days with Soviet trade officials to see if there was a basis for future meetings on a Cabinet-position level between the two countries. Last year, the United States did about $3 billion in export trade with the Soviets but imported only about $500 million in Russian goods. Olmer said his preliminary discussions were used to identify areas in which trade barriers might be removed.