Egyptian President Anwar Sadat, the first of a succession of Arab leaders to confer with President Carter, appealed for U.S. help yesterday in establishing a Palestinian state as the cornerstone of an Arab-Israeli peace agreement.

Standing beside Carter in the East Room of the White House - in a welcoming ceremony moved inside because of rain - Sadat declared that "no progress whatsoever can be achieved so long as this (Palestinian) problem remains unsolved."

Addressing another of the basic elements in the Middle East conflict, Sadat called by implication for Israeli withdrawal from Arab territory occupied in the 1967 war. "You cannot support foreign occupation of one's land or tolerate territorial expansions. We know that attachment to one's land is a value which is deeply rooted in the fabric of the American society," Sadat declared.

The Carter-Sadat conferences, which began immediately after the welcoming ceremony with an-hour-and-40-minute White House meeting, marks the opening of a new phase in the U.S. effort to bring about a new Geneva peace conference on the Mideast later this year leading in time to a comprehensive peace agreement.

The first step was secretary of State Cyrus R. Vance's February trip to Israel and key Arab states. The second step was Israeli Prime Minister Yitzhak Rabin's visit to Washington in early March. Sadat's trip, to be followed by meetings between Carter and leaders of Jordan, Syria and Saudi Arabia, begins the presidential-level discussions with Arab leaders.

Carter declared in welcoming Sadat that "I personally am willing to devote a great deal of own time and the time of the American governemnt" to the search for Middle Eastern peace. Informed sources said Carter told Sadat, as their talks began, that he is placing heavy emphasis on this quest in 1977 because it would be much more difficult in 1978, which is a U.S. election year.

Shortly after the visit of the Israeli prime minister, Carter made known in a press conference and other statements the broad outline of his suggested framework for an Arab-Israeli settlement. The major elements include:

A full peace for Israel, involving recognition of its right to exist and the opening of borders, trade and cultural relations.

Israeli withdrawal from occupied Arab territory, with modifications which Carter suggested at one point would be "minor." Carter suggested that Israel might withdraw in stages over eight years or more, in a schedule coordinated with Arab actions demonstrating the Arabs' commitment to peace. At least for a time, Israel's defense lines might be forward of its eventual permanent borders, Carter said.

A homeland for the Palestinian people who left or were displaced from homes in Palestine after the creation of the Jewish state. Carter has not defined the nature of the "homeland," though he has at times expressed a personal preference that it be part of Jordan.

Leaders of the Arab states are officially committed to an independent Palestinian state to be created on land now occupied by Israel on the West Bank of the Jordan River and on the Gaza strip along the Mediterranean. Sadat suggested in February that formal ties be forged between Jordan and the leadership of a future Palestinian state, even before the conventing of a Geneva peace conference later this year.

Sadat told Carter at the welcoming ceremony yesterday that recent presidential remarks about the Palestinian homeland "came very close to the proper remedy." The Egyptian added. "What is needed is the establishment of a political entity where the Palestinians can, at long last, be a community of citizens, not a group of refugees." Israel, however, is extremely resistant to the idea of a Palestinian state on its borders.

In a recent interview with Business Week magazine, Sadat was quoted as saying that Carter's public statements contained "positive and negative elements" from the Egyptian viewpoint. "I prefer Kissinger's way. This negotiation should be handled discreetly until we reach something concrete," Sadat was quoted as saying.

Presidential press secretary Jody Powell said the question of Palestine Liberation Organization representation at a Geneva conference was discussed by Sadat and Carter, but that no attempt was made to resolve it at this "exploratory meeting." The Arabs back PLO representation at Geneva but the United States - like Israel - has been opposed. The question of the PLO is the main procedural question standing in the way of a new Geneva peace conference.

The current Washington visit and the Middle East peace maneuvering that follows are vitally important to Sadat, who has been in a shaky position at home since riots in January over a suddenly announced austerity program. Many Middle East specialists believe that Sadat must produce early and tangible evidence that his U.S. connection is working to Egypt's benefit in the diplomatic, economic and other fields if he is to remain in power.

Egypt, which has been receiving about $750 million yearly in U.S. economic aid since reestablishment of relations with the United States in 1974, is second only to Israel as an American aid recipient. However, Sadat has said he needs $5 billion to $10 billion more in external assistance in the next several years.

The biggest source of aid to Egypt is Saudi Arabia and other oil-rich Middle Eastern states. The United States has encouraged a meeting next month of some 14 nations that assist Egypt, under the sponsorship of the World Bank.

Sadat, who terminated his military pact with the Soviet Union early last year, has said he will ask the United States for large numbers of "defensive weapons," including 5-5E warplanes and TOW anti-tank missiles. White House and State Department officials said the military supplies did not come up in Sadat's initial conferences here.