The Carter administration is considering a new plan to aid the American steel industry that would automatically slap still tariffs, or extra duties, on imported steel that is sold here below a specific "minimum" price.

The proposal is the centerpiece of a broader package to help domestic steel makers being prepared by a special administration task force headed by Anthony M. Solomon, the under-secretary, of the Treasury for monetary affairs.

The group met yesterday with key administration economic officials, and apparently received broad support for the plan. A final decision on the Solomon recommendation is expected within two or three weeks.

Adoption of the new policy almost certainly would spark protests from abroad. U.S. sources estimated the plan would trim Japan's steel exports here by as much as one-half, and could wipe out European sales here entirely.

Viscount Etienne Davignon, top steel negotiator for the European Common Market, was in Washington yesterday for meetings with Treasury and State Department officials. He will confer today with Solomon and Robert S. Strauss, the President's special trade representative.

The effect of the new Carter plan would be to eliminate present delays in imposition of tariffs for "dumping" - the selling of imports here at a price below their cost of production and transportation.

It has been this long period of delays - often running seven months to a year - that has made industry wary of anti-dumping procedures in the past, and sent steel makers clamoring for import quotas. Carter promised the steel producers last month he would speed up the whole process.

Under present procedures, the government responds to dumping complaints from a domestic industry by conducting a lengthy investigation of whether overseas producers are violating the anti-dumping laws. The process usually takes from seven to 10 months.

The case then goes to the U.S. International Trade Commission, which then must decide whether the domestic industry has been injured by the dumping - a three-month procedure. If injury is found, tariffs are imposed.

The Solomon plan would hasten the entire process by computing a so-called "reference" price for imported steel products, and then in effect assessing duties immediately on any product found selling here below that.

The reference price would be set by taking the production and transportation costs of the most efficient producer in each bloc of exporting nations and treating it as a minimum price for all products in that line.

Officials would establish separate reference prices for European and Japanese producers for every product, to take account of cost differences in those two regions. Reference prices for producers elsewhere would be computed separately.

Administration sources said the White House would not need to push through new legislation to put the system into effect, but could merely revise present procedures on its own.

Under the plan proposed by Solomon, the Treasury simply would satisfy itself that an important steel product was selling here at below its reference price and then "withhold appraisal" on the case - a technical move that would pave the way for temporary duties.

The government would begin collecting these duties immediately, and hold them in escrow pending an eventual ruling by the trade commission. The case then would go to the commission, which would follow its regular procedures.

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Strauss and other high officials have indicated they hope to resolve the steel issue in so-called "sectoral" or sidebar talks under the Tokyo Round trade negotiations now going on in Geneva.

The "reference" price plan would be part of a broader package the administration is preparing to help the domestic steel industry that officials say could include some new tax breaks and postponement of pollution-control requirements.

W. Michael Blumenthal, Secretary of the Treasury, told a television audience Sunday the administration is planning a "three-pronged program" for steel that will try to protect the industry from unfair competition from abroad, help it meet its cash-flow problems and spur new investments.

Officials cautioned yesterday that the Solomon proposal "still has a lot of technical problems that need to be worked out," and is far from completed. However, they confirmed that "there now is a consensus" for making the plan the major element in the upcoming steel package.

The administration has been flooded with anti-dumping petitions from U.S. steel producers in the past two months since officials began inviting the industry to use anti-dumping procedures rather than seeking import quotas.

In all, some 16 separate cases now are pending in the steel industry alone. The industry previously had been reluctant to use the anti-dumping process because it involved so much time and domestic charges usually were rejected.