Leaders of Egypt and Israel agreed last night on separate pacts governing the Sinai, the West Bank and Gaza Strip at the Climax of 13 days of U.S.-sponsored talks at Camp David, Md.

The agreement was announced by the White House about 90 minutes before Israeli Prime Minister Menachem Begin and Egyptian President Anwar Sadat were to meet with President Carter in the East Room to make public their agreement.

Full details of the new agreements will not be made public until today, according to White House officials, who spoke of them in optimistic terms as a "significant step forward" on the road to peace.

However, the officials made clear that a major disagreemet remains between Israel and Egypt over the Israeli settlements in the Sinai and refused to say whether this pact will take effect in the event that it remains unresolved.

Implementation of the pact regarding the West Bank depends on the cooperation of Palestinians living in that region as well as agreement by Jordan, which has not been a party to the negotialtions. U.S. officials expressed the hope last night that Jordan would concur. But there was no claim that Jordanian compliance had already been obtained.

The question of sovereignty for the Gaza Strip remains a matter for negotiations between Israel, Egypt and the Palestinians living in the area.

The Egyptian-Israeli pact covering the Sinai is to be signed within three months from now, U.S. officials announced. The first major Israeli withdrawal from the Sinai is to take place within three to nine months after that. Normal relations between Israel and Egypt are to be established at the time of this first withdrawal, U.S. officials said.

Official statements issued last night indicated that Egypt intends to go ahead with the Sinai pact whether or not the more complex West Bank agreement comes to fruition.

The agreements emerged from the 13-day negotiations, during which the Carter administration imposed a strict news blackout at the president's remote retreat in the Catoctin Mountains.

Carter appeared to focus his attention and efforts during the final day on Sadat, who entered the summit asserting that he would not accept a partial agreement leading to the kind of detailed and lengthy talks that Begin insists are necessary for an eventual peace agreement.

The president met with Sadat twice, for a total of nearly two hours. Between those sessions, he called on Begin for a six-minute discussion. Carter had launched his final drive for a "framework" for future Arab-Israeli talks by talking 4 1/2 hours with Begin on Saturday night.

The meeting with Begin which did not break up until 12:30 yesterday morning, was described by Israeli officials as "good" and "businesslike," giving rise to a glimmer of optimism among the reporters who have been covering the summit from an American Legion hall here six miles east of Camp David.

As the summit came to a close, Carter, Begin and Sadat were each preparing for the next stage of the Middle East efforts, the public explanation to U.S. and world opinion of what they have and have not achieved over the past 13 days.

Both Sadat and Begin are expected to spend today and tomorrow in Washington, where they will brief congressional leaders separately and give interviews to each of the three major commercial television networks. Sadat is also due to hold a press conference.

On Capitol Hill, each will brief the Senate Foreign Relations Committee and will meet with other senators and representatives in more informal sessions, according to diplomatic sources.

Carter yesterday postponed an address to the United Steelworkers' convention in Atlantic City from tomorrow to Wednesday, amid unconfirmed reports that he plans to address a joint session of Congress tomorrow night. U.S. sources here in Thurmont said no decision had yet been made on such an appearance by the president.

Sadat will leave the United States for Morocco Wednesday, an Egyptian embassy spokesman said, and may brief Jordan's King Hussein, who is due to arrive in Rabat today.

Begin will go to New York, probably on Wednesday, to meet American Jewish leaders there and to give more media interviews.

In yesterday's editions, Egyptian and Israeli newspapers stressed the importance of the struggle over world opinion that would follow the summit. In the media battle to come, "it will be worthwhile to expose the views of all the sides and certainly to point out the American method of presenting the case," Hatzofeh, organ of Israel's coalition National Religious Party, wrote.

For Carter, the summit represented the most concentrated and intense single effort of his presidency. For almost two weeks, he virtually ignored the other business of government, which he turned over to Vice President Mondale. Even then, he called Mondale into help in the talks at crucial stages.

Carter kept by his side during the two weeks Secretary of State Cyrus R. Vance, national security adviser Zbigniew Brzezinski, spokesman Jody Powell and the administration's top Middle East experts.

The Camp David summit's 13-day run made it one of the longest presidential level meetings of recent history. It exceeded by four days the Yalta Conference of 1945, at which Franklin D. Roosevelt, Winston Churchill and Joseph Stalin effectively decided upon the post-World War II global balance of power.

The Potsdam conference that same year lasted three days longer than the Camp David Middle East summit. In contrast, when Dwight D. Eisenhower met Nikita S. Khrushchev at the retreat in the Catoctin Mountains in 1959, the leaders of the world's two superpowers conferred only for two days.

The road to the Camp David summit on the Middle East began in one sense with Sadat's dramatic decision to go to Jerusalem last November in what he said was an attempt to break down the psychological barriers that had resulted in four wars in 30 years in that region.

The Israelis joined the rest of the world in hailing Sadat's trip as an act of great courage and statemanship. It broke irrevocably with the Arab strategy, and belief, of treating Israel as an outlaw nation that the Arabs would never recognize.

The trip split the Arab world into even hostile factions, aligning Syria more firmly with countries like Libya and Iraq that were already hostile to Sadat's decisions in 1974 and 1975 to sign interim peace agreements on the Sinai peninsula with Israel.

In a concession larger than previous Israeli governments had been willing to make, Begin indicated he would return to Sadat sovereignty over all of the Sinal peninsula if they could reach a final agreement. With Syria on the sidelines, the fate of the Golan Heights was not directly involved.

But Sadat's initative seemed to run aground almost immediately upon the West Bank territory of the Jordan River, ruled by Jordan until the 1967 war. Begin referred to the territory inhabited by 1.1 million Palestinians by the Bibical names of Judea and Samaria, and asserted that he would never surrender control over parts of biblical Israel.

Instead, at a meeting with Sadat at Ismailia in December, Begin presented Israel's 26-point plan for the West Bank. It proposed local "autonomy" for Palestinians on the West Bank for five years and the maintaining of Israeli troops and settlements. Most importantly for Sadat, it offered nothing on the question of ultimate sovereignty.

The talks ended in disagreement over these points, and lower-level talks over the following months also failed to make any progress. Carter openly criticized Begin for lacking flexibility in the takls during a March visit to Washington, and Sadat renewed his calls for the United States to become directly involved in the negotiations and put preasure on Israel to force a settlement.

But in July, after a foregin ministers' meeting at Leeds Castle in England involving Israel, Egypt and the United States, Sadat reportedly became concerned that the Carter administration was joining Israel in a strategy of stretching out talks in order to buy time rather than to reach a settlement. On July 30, after ordering the Israeli military liaison mission out of Egypt, he declared that there would be no further Egyptian-Israeli talks unless Begin agreed in advance to full withdrawal from the Arab territories occupied in 1967.

Concerned that continued stalemate would undermine the position of Sadat and eventually of other friendly Arab governments, including Saudi Arabia, Carter decided on his own to invite both leaders to come to Camp David, even though some of Carter's top advisers were skeptical that a summit with no advance preparations could succeed.

Carter set out to revive the direct negotiations and to produce a framework for an Arab-Israeli peace agreement. He insisted on a total news blackout, which lasted until the closing days did not set a deadline for the negotiations. Finally, on Friday, with Sadat and Begin still deadlocked on the question of sovereignty, he got the two leaders to agree to finish the conference last night.

After the first three days of the conference, which were described by participants as being conducted in a very good atmosphere, preiods of tension appeared to develp. Sadat and Begin, who had come 6,000 miles to talk, did not meet formally from Sept. 7 until last night.

Instead, Carter shuttled between the two men, meeting them and their aides in a constant stream of negotiations. The White House completely controlled the trickle of information that came out, largely through the photographs taken by official photographers and sparse scheduling details relayed in daily briefings by Powell.