The Reagan administration has no plans to dismantle or modify the trigger-price mechanism protecting American steel prices, Lionel H. Olmer, new Commerce Department undersecretary for international trade, said in an interview yesterday.

The administration is committed to the trigger-price system, which is intended to set off an investigation when foreign steel is sold here below a specific price. "There's no tinkering with the TPM," Olmer said.

The system became controversial last year when U.S. Steel Corp. accused steel makers from seven European countries of selling steel here below what it costs them to make it, spurring an investigation by the Commerce Department and the International Trade Commission. The government then suspended the trigger prices until an agreement was reached with U.S. Steel to drop the complaints.

U.S. Steel contended that if the trigger-price system failed to work again, it would file the complaints again.

Administration sources have said there was a movement within the administration to dismantle the controversial trigger-price system because it wasn't working properly. European steel producers have complained recently that because of the strong dollar they are able to produce and sell steel at prices lower than they are allowed to sell it here. They blame the trigger-price system for their current slump. So far four foreign steel makers have asked to sell steel here below the trigger prices.

But a move to dismantle the system probably would lead to more politically embarrassing complaints from U.S. Steel, the sources said.

During an interview in his office, Olmer emphatically said the administration is committed to making the trigger-price system work.

"We're committed to administering the system as fairly, objectively and efficently as possible," Olmer said. He added that the United States, Japanese and European steel industries want the system and view it as "an effort at determining an acceptable level of discomfort."

Olmer said the Commerce Department should have a decision by mid-July on whether to allow the four foreign steel makers to sell their steel here below the trigger prices, a system called preclearance. The trigger-price system "would fall apart if too many preclearances are approved," Olmer said. "You can't have a TPM system and have half the people covered by it" not following it.

Olmer, who has been undersecretary for about one month, said he expects an administration study of East-West trade to clear up ambiguities in what goods U.S. businessmen can sell to the Soviet Union and Eastern bloc countries. The Soviet satellite countries each will be treated differently, but the criteria for determining their treatment will be decided by the State Department and then a Cabinet-level committee, he said.

Many American businessmen have complained that U.S. officials are too slow in approving export licenses to sell their goods to the Soviets or Eastern bloc nations and that the Europeans are more efficient and therefore have a competitive advantage over Americans, Olmer said.

The administration also is concerned with diversion to the Soviet Union of goods sold to Eastern bloc countries, Olmer said."We have to be assured that if we authorize the sale of equipment to" one country "it doesn't get diverted," he said.

Olmer, former director of international programs for Motorola Inc., said he particularly is interested in competition with the Japanese in telecommunications and opening up markets in Japan for U.S. firms. "Japan and high technology are my special interests," Olmer said.

Next week Olmer will lead a group of 75 businessmen to Japan to help them export more to the country.

In addition, he said he will devote his time to encouraging the 20,000 to 30,000 small and medium-sized businesses to increase exports.