The cost to the American taxpayers of the Egyptian-Israeli agreements negitiated by President Carter will be about $5 billion in new U.S. military and economic aid to the two nations over a three-year peried, White House officials said last night.

In addition, written assurances are being prepared dealing with U.S. security commitments and other arrangements, similar to the documents supplied to Egypt and Israel by then-secretary of state Henry A. Kissinger in the Sinai disengagement agreement of September 1975, according to officials.

Members of Congress who were informed late yesterday at the White House of estimates of the costs and commitments said they appeared more modest then anticipated, and predicted that Congress would approve the necessary legislation.

"If this is a fair estimate of the cost, it's a real bargain," said Senate Minority Leader Howard H. Baker Jr. (R-Tenn.), whose sentiment was echoed by other lawmakers.

Carter was quoted by lawmakers as saying that no military treaty with either nation is contemplated at the present time, despite speculation to the contrary.

The implications of Carter's central role as well as his explicit assurances add up to a deepening U.S. involvement in guaranteeing the success of an Egyptian-Israeli peace treaty. However, officials said there are no plans to station U.S. combat forces in the area.

Israel suggested that the United States take over at least one of the two air bases that must be vacated as the Sinai is returned to Egypt, and the proposal reportedly has been seriously considered. However, Egypt has made clear its opposition to such an American base, and the idea apparrently is dead.

New military assistance of about $4 billion over three years, will be divided between Egypt and Israel, mostly to purchase weapons on lists negotiated with the two sides by Secretary of Defense Harold Brown, who accompanied Carter to the Middle East.

The weapons and security negotiations carried on by Brown and the Egyptian and Israeli defense ministers are believed to have played an important role in the success of the parallel political talks.

The weapons to be sold to Egypt were described as replacements for some Soviet-supplied weapons, now antiquated, which have been the backbone of the Egyptian military force. Some naval and air defense weapons and transport aircraft are reportedly to be sold, but not the most up-to-date high-performance airplanes, such as the F15 or F16.

The weapons for Egypt will be the first financed by the Untied States for that country. Previous sales of C120 transport planes and F5 jet fighters were financed by Saudi Arabia. The United States is also considering its first military grant aid to Egypt.

The weapons for Israel evidently are from the unfilled shopping list supplied to the United States months ago. The United States has furnished military credits to Israel of about $1 billion annually in recent years. The new military aid will be in addition to this.

Congressional sources said the United States agreed, in the phased withdrawal of Israel from the Sinai, to help Israel relocate its two air bases and to assist both sides to relocate seven or eight military divisions. Some of the military assistance is reported to be in compensation for these costs.

Perhaps $1 billion in additional economic aid to the two countries over several years is also contemplated, according to officials. Lawmakers were told this aid will be for food, housing, sewage treatment, water projects and a telephone system for Egypt.

White House officials emphasized that many details remain to be worked out, and thus the figures represent only rough estimates. Israel currently receives about $8000 million in economic aid yearly, and Egypt about $1 billion, including food aid.

A major imponderable in connection with aid to Egypt is whether Saudi Arabia and other Persian Gulf nations will continue their subsidies to the regime of President Anwar Sadat, in view of their disapproval of a separate Egyptian-Israeli peace treaty.

The Arab states reportedly agreed at Baghdad in November to cut off all assistance to Sadat if and when an Egyptian-Israeli treaty is signed. Kuwait, one of the major donor states, yesterday called for implementation of the Baghdad resolutions.

Following the White House briefing, lawmakers quoted Carter as saying that "strong representations" have been made to Saudi Arabia about continuation of its aid to Egypt. There have been reports, which have not been officially confirmed, that the United States will make up the difference to Egypt if the Saudis cut off their assistance, which is estimated at about $1 billion yearly.

One official said European nations and Japan might be asked to participate with the United States if it were necessary to make up the difference for a reduction of Saudi aid.

In response to a question, lawmakers were told that Saudi Arabia is expected to go ahead with paying for 50 F5 jets for Egypt that were approved last spring.

Carter briefed about 50 lawmakers in the East Room for about an hour on the negotiations and U.S. commitments. Secretary of State Cyrus R. Vance took part in the briefing, and other high officials were on hand.