The Carter administration said yesterday that Egypt has decided to postpone buying the F15, the top-line U.S. jet fighter that President Anwar Sadat is eager to acquire and that the United States has agreed in principle to sell to the Egyptains.

Although U.S. officials refused to say so publicly, the arrangement represents an attempt to satisfy Sadat's symbolic need to claim access to sophisticated U.S. weapons without arousing Israel's opposition to the point where its supporters in Congress would fight strongely against a U.S. plan for reequipping and modernizing the Egyptian armed forces.

As the first step in this long-range program, the administration announced yesterday it will sell the Egyptains 40 of the less sophisticated F16 fighters 250 M60 tanks and a variety of other weapons and military equipment.

The U.S. decision to provide Egypt with F16 planes and M60 tanks had been revealed earlier as part of the administration's reassessment of its Middle East arms policies in the wake of the Soviet invasion of Afghanistan.

To help contain Soviet moves in the Persian Gulf region, the administration has been seeking to increase its military aid to friendly governments in the Middle East and Southwest Asia. That Included a major commitment to Egypt, which is America's closest friend in the Arab world.

However, the U.S. program for Egypt, tentatively expected to provide Sadat with approximately $4 billion in military credits over five years, had stirred considerable concern in Israel. The Israelis, despite their peace treaty with Egypt, fear that Sadat could be replaced by a more a radical Moslem leadership that would repudiate the treaty and use Egypt's new U.S. weapons in a war against Israel.

As a result, the administration in its efforts to balance its relations with both countries, found itself caught in a squeeze that became symbolized by the F15, the most advanced fighter in the U.S. arsenal.

Sadat, whose rapprochement with Israel has isolated Egypt from most of its traditional Arab allies, made clear that he had to demonstrate to the Arab world that he had access without restrictions to the same ultra-sophisticated weaponry that the United States has supplied to Israel. That, the Egyptians insisted, had to include the F15, which is being provided to the Israeli air force.

However, the Israelis had made clear that if Egypt got the F15, they would seek through their congressional supporters to try to block the entire U.S. move toward a close arms supply relationship with Egypt. Conversely, the Israelis informed Washington, if the F15 was kept out of Egyptian hands, they would soft pedal their opposition.

The U.S. bid to get around the problem was worked out by Assistant Secretary of Defense David McGiffert during recent talks in Cairo. McGliffert told the Egyptains that the United States would sell them the F15, but he cautioned them that it would be four years before the could expect the first deliveries.

In addition, McGliffert is understood to have pointed out that the cost of a squadron of F15s -- roughly $1.5 billion -- would use up much of the credits Egypt will get from the United States, that the Egyptians would find them difficult to maintain without bringing in large numbers of U.S. Air Force technicians and that Israeli opposition could jeopardize the effort to get other arms aid for Egypt through Congress.

In the end, according to U.S. sources, the Egyptians, after weighting these arguments, decided to settle for the symbolic principle of the U.S. promise that they can have the F15s if they want them, but to defer buying them for the time being and use their available U.S. credits for other items.

Following the Egyptian-Israeli peace treaty last spring, the United States put together a special military aid package for the two countries that promises Israel an additional $3 billion in credits and grants over three years and that gave Egypt $1.5 billion in credits to be disbursed in increments of $500 million annually in the 1979, 1980 and 1981 fiscal years.

Then, in the wake of the Afghanistan crisis, the United States decided to beef up its Egyptian aid. It asked Congress to approve an additional $350 million in military credits to make the total request for fiscal 1981, which begins on Oct. 1, $850 million, and it promised Egypt to increase the request for fiscal 1982 to $800 million.

Administration sources have said privately that the tentative plan is to continue granting credits at this $800 million annual rate for at least three additional years -- a total of $4 billion over a five-year period.

In announcing the sales of F16s and M60s and other equipment yesterday, State Department spokesman Hodding Carter said that working out of final details and consulations with Congress prevented putting a dollar figure on the total value of the package at this time. He added that it also was not possible to specify yet when the equipment will be delivered to egypt.