The Reagan administration has notified leading members of Congress that it is seriously considering asking for special legislation to permit stationing 1,000 or more U.S. troops in the Sinai, the first permanent ground combat presence of this country in the volatile Middle East.

The administration's formal position is that no final decisions have been made and that, in view of complicated and touchy problems involved, a clear-cut request to Capitol Hill is weeks, perhaps even months, away.

Nonetheless, sources familiar with the developments said the administration appears to be moving closer every day in internal policy-making and diplomatic discussions to agreement on such a plan.

When and if it is sent to Capitol Hill, a proposal for stationing U.S. forces in the Sinai is likely to generate intense debate. Several lawmakers have made known their misgivings about having American troops stationed as a highly exposed "tripwire" in such a touchy area.

The U.S. troops would be part of a multinational force to police the Sinai after the major Israeli withdrawal scheduled for April 1982 under the Camp David accords.

Secretary of State Alexander M. Haig Jr., in testimony to the House Foreign Affairs Committee last Wednesday, expressed doubt that Israel will withdraw unless a peace-keeping force polices its sensitive border area with Egypt. Haig added that "some American participation" may be required.

As presently conceived, the proposed American contingent would be the core of the multinational force, and the United States, directly or indirectly, would contribute most of its $50 million annual upkeep.

In an effort to make a greater showing of other flags, U.S. diplomats are scouring the world for other nations that might be persuaded to contribute to the Sinai patrols in the face of likely objections from politically important Arab nations opposing the Camp David agreements.

Among contributions being suggested are Nepal, the landlocked mountain kingdom between India and China, and the Fiji islands in the far Pacific. Both have contributed troops to the U.N. peace-keeping force in southern Lebanon, but diplomatic sources said it might be more difficult to arrange contributions outside of the U.N. framework.

The Camp David treaty calls for a U.N. force to supervise the Sinai after the Israeli withdrawal, but President Carter promised Israel that the United States would arrange for the job to be performed by a multilateral force if the United Nations could not participate.

The Soviet Union indicated in late 1979 that it would veto U.N. sponsorship of a Sinai force in connection with Camp David.

Egypt, which would prefer U.N. auspices for the Sinai peace-keepers, has launched discussions of such a plan recently with Secretary General Kurt Waldheim and permanent members of the U.N. Security Council, which includes the Soviet Union.

At the same time, however, Egyptian and Israeli officials have been meeting with Deputy Assistant Secretary of State Michael E. Sterner on the U.S.-sponsored "multinational force."

Sterner is scheduled to leave Washington later this week for another round of talks on the issue in Cairo and Jerusalem, amid hopes here that an "understanding" about a multinational force can be completed during Haig's trip to the Middle East less than two weeks from now.

Among the most sensitive issues are the limits and locations of a U.S. force. Some Washington policy-makers would like to see American troops in the Sinai take on a dual role, part of which would be akin to that of the Rapid Deployment Force in exerting U.S. power in the Persian Gulf.

Such a role would be enhanced if the United States were to inherit the two large Sinai air bases to be vacated by Israel. To date, however, Egyptian President Anwar Sadat has resisted such U.S. use of the Sinai bases.