Administration officials yesterday dismissed claims that a special plan to set minimum prices for imported steel is illegal and spent much of the day putting the finishing touches on a five-part program to aid domestic steel makers.

Treasury Undersecretary Anthony M. Solomon, who heads an interagency task force developing the plan, presented the proposal to the President yesterday afternoon.

Administration officials expect the President to formally approve the program today. If he does the detailed plan will be released to the public this afternoon.

The plan is reported to include:

Minimum prices for imports of steel products, with the prices based on the costs of the most efficient foreign steel producer. If the imports come in below the mininum price, a speeded up anti-dumping investigation will be launched by the Treasury Department. If the agency determines that the product is being sold below cost it will levy a special duty.

A special $215 million loan guarantee fund, administered by the Commerce Department's Economic Development Administration, to help modernize domestic steel plants located in areas of high unemployment.

A call for a relaxaton of some antitrust rules to permit steel companies to engage in joint ventures to permit them to build bigger, more efficient facilities such as blast furnaces.

Proposals to help steel makers write off the cost of their equipment, especially anti-pollution devices more quickly.

The plan also calls for changing transportation regulations to permit steel to be shipped more cheaply and looks at ways to help steel companies meet anti-pollution guidelines.

Top Treasury officials said that a claim by the general counsel of the International Trade Commission that elements of the steel plan are extralegal and may violate antitrust law is unfounded.

The International Trade Commission is also considering whether to take action on its own to restict steel imports, which could prove more of an embarrassment to the president than a real hindrance to putting the plan into effect. The President has days to reject any action by the commission.

THe trade commission, former known as the Internaitonal Trade Commission, administers many [WORD ILLEGIBLE] of the Trade Law of 1974. It also [WORD ILLEGIBLE] rule whether an industry is being damaged in cases where the Treasury finds dumping violations.

The six-member commisison [WORD ILLEGIBLE] meet Dec. 15 to discuss whether proceed on its own against steel imports from Europe. If it finds European producers guilty of unfair trade practices - and officials say that it not clear whether dumping is an [WORD ILLEGIBLE] trade priactice under the terms of [WORD ILLEGIBLE] law - it could stop imports of [WORD ILLEGIBLE] product.

At the request of ITC Commissioner Catherine Bedell, the general counsel's office said that by effectively setting minimum prices[WORD ILLEGIBLE] steel, the proposed administration program would violate antitrust law.

But Treasury officials said that the Justice Department and its antitrust division have reviewed the plan and find no legal problems with it.

Officials said the Treasury expect to publiosh proposed regulations together with the first set of minimum prices, by the middle of the month and plan to put the plan in effect [WORD ILLEGIBLE] Feb. 1.