President Carter already has sketched out to the Soviet Union options for reducing strategic nuclear weapons below the target set by former President Ford and Soviet leader Leonid I. Brezhnev.

The President suggested various formulas for cutting nuclear force levels in his meeting Tuesday with Soviet Ambassador Anatoliy F. Dobrynin, it was learned. Formal U.S. proposals, which Secretary of State Cyrus R. Vance is to discuss with the Soviet leaders in Moscow starting March 28, are now being developed. The National Security Council's Special Coordinating Committee met on this subject yesterday.

Vance said in an interview yesterday that in Moscow he will discuss cuts in both nuclear and conventional weapons, as well as curbs on arms sales.

The President, in effect, gave Dobrynin a preview of the direction in which the Carter administration would like to go in limiting nuclear arms.

Although details of the Carter suggestions are undisclosed, they would, as the President has said publicly, reduce the maximum level of 2,400 nuclear missiles and bombers for each nation, fixed in the Ford-Brezhnev talks at Vladivostok in November, 1974.

A cut of about 10 per cent from that ceiling was included in a proposed accord which former Secretary of State Henry A. Kissinger reached in Moscow in January, 1976.

The Kissinger-supported formula became stalled in the controversy it was intended to overcome. That is, how to deal with two weapons systems not resolved at the Vladivostok meeting. They are Soviet bombers, known in the West as Backfire bombers, and American-initiated, long-range cruise missiles. They remain the two principal barriers in the strategic arms limitation talks (SALT).

President Carter discussed with Dobrynin various mixes of force levels for intercontinental missiles and bombers that could cut arms ceilings of 2,400 on a side by more than 10 per cent.

The President publicly has said he would like "to move very quickly, even prior to the SALT II agreement, toward a much more substantive reduction in atomic weapons . . ."

Brezhnev, however, has said that the Soviet Union believes it will "further complicate" agreement on a new SALT pact if negotiations on force reductions are added at this stage. He said reductions should be taken up later.

Nevertheless, the Carter administration is attempting to induce the Kremlin to take a new look at the case for earlier reductions. One U.S. argument presumably will be that cuts in the Vladivostok arms ceiling were contemplated in the Brezhnev-Kissinger discussions last year.

The Carter-Dobrynin discussions, and the Vance interview yesterday, are cited as double illustrations of the Carter administration's determination to press strongly on the arms control issue. The nomination of Paul C. Warnke, a champion of arms control, to head the U.S. Arms Control and Disarmament Agency, is an integral part of this strategy.

Administration officials say they fully recognize that the dispute over Warnke's nomination will be a congressional test of the President's ability to marshal support for this major element of his foreign policy. They express confidence that Warnke will be confirmed, but do not minimize the opposition's determination to try to challenge the evolving Carter arms control policy by attacks on Warnke.