The Carter administration has formally briefed Japan on the plan it is considering to set minimum prices for most steel imports here, but apparently has received no official reaction.

The briefing came in talks here this past week between Hiroshi Kanaski, a spokesman for the Japanese Ministry of International Trade and Industry, and key U.S. trade officials.

It was not immediately known whether the Japanese would oppose the American plan, which calls for automatically slapping stiff tariffs, or extra duties, on imported steel sold here below a specific price.

European trade officials, told of the plan separately in talks here earlier this week, reacted favorably to the idea. Their only major concern was that they be consulted fully before the minimum prices are set.

The plan, still not decided finally, is being drafted by a special administration steel task force headed by Anthony M.Solomon , undersecretary of the Treasury ofr monetary affairs. It is expected to be unveiled soon.

U.S. officials said yesterday they expect to be notified of the Japanese reaction to the settl proposal within the next two weeks. Tokyo traditionally waits several days begore reacting formally to any measure.

Meanwhile, domestic problems involving the steel industry continued to mount, with the U.S. Steel Corp. predicting if the government does not help soon, much of the nation's steelmaking capacity could be shut down.

David M.Roderick, the company's president, said U.S. Steel was prepared additional "dumpling" cases against several unidentified European steel firms, and will file them shortly.

Dumpling refers to the practice of some foreign producers of selling their products here at below the cost of production and transportation. The move is illegal under U.S. trade law.

Separately, the Labor Department announced it has certified 3,500 workers in Lackawanna, N.Y., to receive benefits under the so-called adjustment assistance program because they have been forces out of jobs due to imports.

The workers all are former employees of the Bethlehem Steel Corp. plant or the South Buffalo Railway Co., 'a Bethlehen subsidiary. Bethlehen announced the layoffs in August. The benefits could reach $208 a week for each worker.

At the same time, WilliamA.Sullivan Jr., president of a steel industry coalition in Pittsburg, said he has proposed a plan to federal officials to give laid-off workers in Youngstown, Ohio, $80 million to buy back their plant.

Sullivan said he had discussed the proposal with the Solomon task force and it was being considered. Treasury officials declined to comment on the move.