Egyptian President Anwar Sadat, undaunted by President Reagan's rejection of his proposal for U.S. contact with the Palestine Liberation Organization, yesterday called for action to encourage an emerging sense of responsibility of the part of the Palestinian leadership.

In an address to the Council on Foreign Relations in New York, Sadat said Palestinian cooperation with the United States in the recent cease-fire in Lebanon was "a clear indication that the leadership of the Palestinian movement has begun to assume its responsibility undeterred by pressure or intimidation."

He added, without being specific, that "we should do all that we can" to encourage the Palestinians and Saudi Arabia, which played a key role in the cease-fire. Their continued pursuit of this path, Sadat said, would bring "tangible progress on the road to peace."

Despite the recent history of bitter contention with the Palestinians and Saudis, Sadat has praised both consistently for the cease-fire since a London news conference early this week.

At a Senate luncheon Thursday, the Egyptian president went out of his way to urge U.S. lawmakers to approve sale of sophisticated radar surveillance aircraft, the AWACS, to Saudi Arabia on political and military grounds, according to congressional sources.

In yesterday's address, the text of which was released by the Egyptian Embassy, Sadat charged Israel with "military adventures in Iraq and Lebanon," presumably referring to Israeli bombing raids against the nuclear reactor in Iraq and against Palestinian encampments and Beirut headquarters in Lebanon.

He expressed concern that such Israeli action could "drive a wedge between the peoples of many Arab countries and the United States" and serve the interest of the Soviet Union and its surrogates.

At the same time, Sadat told the foreign relations organization that "I remain optimistic and hopeful" about the cause of peace in the East.

In another section of his address, he attacked "the racist regime in South Africa" for maintaining its control of the mineral-rich territory of Namibia despite United Nations demands to the contrary.

Sadat appealed to the United States and its West European allies to "bring more pressure to bear on South Africa" to comply with the U.N. demands.

Sadat said that he had expressed this view in his discussions this week with the Reagan administration and that he expects "a prompt response." Sadat's view of South Africa and Namibia was not mentioned in any news briefings by administration officials on the talks.

Egypt, an African as well as a Middle East country, is a member of the Organization of African Unity, and takes an active interest in African affairs.

Egypt is reported to have supplied significant amounts of Soviet military equipment, acquired in the bygone days of its Soviet military connection, to Zambia, Zimbabwe and the Angolan rebel movement headed by Jonas Savimbi.

Sadat attacked the Soviet Union for intervening in the domestic affairs of other nations. At the same time, he called on the West, especially the United States, to "support liberation movements everywhere."

Before flying to New York, Sadat, in a brief address to the U.S. Chamber of Commerce here, appealed for American business support.

The business organization took the occasion to announce formation of a joint American-Egyptian Chamber of Commerce and Industry, with headquarters in Cairo. The chamber said the group was five years in formation.

In New York, Sadat met for 30 minutes with former president Richard M. Nixon at the residence of the Egyptian representative to the United Nations. Nixon told reporters he was optimistic about the Middle East situation, saying: "As time goes by, progress will be made."