Foreign Minister Moshe Dayan suggested yesterday that Israel may harden its opposition to relinquishing airfields in the Sinai if the United States proceeds with the sale of F15 jet fighters to Saudi Arabia.

Making his case in a press conference after meetings with President Carter and Secretary of State Cyrus R. Vance, Dayan charged that the proposed sale of 60 sophisticated war-planes to the Saudis would "have an effect on the entire military picture, our own defensivle borders and our military installations." He volunteered that in these circumstances, giving up some of the Sinai airfields will become 'a major problem.

In its peace plan presented to Egyptian President Anwar Sadat, Israel proposed to return the occupied Sinai to Egypt but also insisted that Israel be permitted to retail control of three Sinai airfields.

Sadat rejected this idea, but there have been unofficial reports that some progress has been made toward a compromise in military talks between the two nations.

Dayan linked the Saude sale to the negotiations by saying the Sinai airfields might be needed to protect Israel from Saudi jets operating from Tabouk airbase not far from the Israeli border. From there the Saudi jets, which are scheduled to be delivered beginning late in 1981, "would be a major undertaking requiring U.S. cooperation."

The State Department letter also said F15s for Saudi Arabia "would not alter the basic Middle East arms balance" and that "fundamental inhibitions which have led Saudi Arabia to refrain from combat with Israel in past conflicts would still pertain."

While making a strong attack on the planned U.S. jet sale to Saudi Arabia, Dayan said nothing to reporters about the proposed U.S. sale of shorter-ranged F5E fighter-bombers to Egypt. This suggested that Israel is reserving most of its U.S. political clout for the battle against the Saudi planes.

Dayan reported he told Carter and Vance that the main case against the warplane sales to the Saudis would be made by Israeli Defense Minister Ezer Weizman, who is due in Washington in early March. The argument may also be taken to the American public by Prime Minister Menachem Begin, who will come to Washington March 14 and 15, according to a statement by Carter yesterday.

While expressing "deep concern" over U.S. positions about arms sales, Israeli settlements and Israeli withdrawal from the occupied West Bank, Dayan also called on the United States to continue mediating in the Middle East and declared, "Without the United States we cannot achieve an agreement with the Arabs."

There was no indication that yesterday's talks at the State Department and White House narrowed the gaps between Israel and Egypt on the peace process, or between Israel and United States. U.S. officials called the meetings with Dayan "stock-taking" sessions rather than negotiations designed to break new ground.

In his midafternoon press conference, Dayan stood firm against giving up Israeli civilian settlements in the Sinai as part of a peace deal with Egypt, but invited Egyptian counter-proposals.

The immediate diplomatic problem, Dayan made clear, is not arms sales or the Sinai but the West Bank.

"In the next few months," he said, King Hussein of Jordan will have to decide whether to join the Egyptian-Israeli negotiations. Dayan expressed optimism that the problems with Jordan and residents of the West Bank could be solved if Hussein will participate, but took a hard position against advance assurances to Jordan about the outcome of the negotiations. He called this "the demand for preconditions."

If Jordan will not join, Sadat will then have to decide whether to make a separate deal with Israel or give up his peace initiative, Dayan said. His remarks indicated that Israel has not given up hope for a bilateral deal with Sadat in the long run.