President Carter's Middle East envoy, Sol Linowitz, conceded today that next May's deadline for setting up an autonomous Palestinian administration on the occupied West Bank may not be met.

At the same time, Linowitz stressed the determination of President Carter and the leaders of Egypt and Israel to persevere despite the slow progress so far in the seven-month-old negotiations set up under terms of the March 26 Egyptian-Israeli peace treaty.

His carefully balanced briefings came after more than two hours of talks with President Anwar Sadat, his first contact with the Egyptian leader since talking over as chief U.S. negotiator. Taken together, they illustrated the 66-year-old attorney's cautious approach to the talks, in contrast to the folksy style of his predecessor Robert Strauss.

After his two days of talks here, Linowitz flew on to Isreal tonight for what he called a similar "learning experience" with Prime Minister Menachem Begin and the chief of the Israeli negotiating team, Interior Minister of Josef Burg.

Upon arriving in Tel Aviv, Linowitz said the U.S. commitment to Israel's security had never been as strong as it is now.

His Middle East tour, the first in his new job, has fallen under the cloud of the turmoil in Iran, the preoccupations in Washington with the fate of the American hostages in Tehran and fallout in the Persian Gulf from the confrontation between the United States and Iran's new Islamic government.

Egyptian officials have expressed concern that the Iranian crisis is distracting Carter and his top Middle East aides in the White House and State Department away from the Egyptian-Israeli negotiations. At the same time, they see the American presidential elections as a likely obstacle to high-level decisions on the Middle East or any U.S. pressure on Israel to make concessions in the talks.

Linowitz emphasized that Carter, in a conversation in Washington, expressed continuing concern for the autonomy negations and the need the carry through on the peace process outlined at Camp David despite the Iranian drama. But, again balancing his remarks, he also acknowledged that the Iranian crisis has affected the talks and indicated that he and Sadat had discussed the fallout in their talks at Sadat's country home 15 miles north of Cairo.

"Obviously the developments in Iran do have repercussions and some of them will be felt in the negotiations in which we are engaged, if only because it will affect this part of world," he said.

Sadat, swiftly moving into the first-named relationship that has become his trademark, said he had spent "a really charming time with Sol," but avoided questions about the substance of their discussions.

"Let us hope that in the near future and with the help of our full partner President Carter and his envoy Sol we can reach full agreement on full autonomy and Jerusalem," he added.

"(Sadat is scheduled to hold a three-day summit conference with Begin Jan. 7 at the Egyptian resort of Aswan, it was announced Sunday in Cairo and Jerusalem, Reuter reported.

[Earlier reports had quoted Sadat as saying Begin's visit would begin Jan. 4 and Begin had last week mentioned to European diplomats a date of Jan. 1.There was no immediate explanation for the apparent confusion over dates.]

Another round of autonomy talks in Israel is slated shortly before Sadat and Begin meet next month in Aswan, taking as its starting point reports prepared by technical teams that have been meeting over the last several months.

Linowitz suggested after his discussion with Sadat that the Aswan summit conference could give new impetus to the autonomy talks, saying Sadat had expressed to him an intention to turn the meetings with Begin into a substantial exchange. In particular, the U.S. envoy said, Sadat intends to pursue some "clear ideas" on resolving the dispute over Jerusalem's status in the proposed Palestinian administration.

Observers in Cairo quickly recalled, however, that Sadat had made previous expressions of intent before past summits with Begin without anything coming of it during the actual meetings.

Jerusalem is regarded as the thorniest aspect of the Palestinian autonomy negotiations. After conquering the entire city during the 1967 war, Israel annexed it, made it the Israeli capital and vowed never to relinquish it. Egypt has maintained, however, that the Arab part of Jerusalem was part of the West Bank before 1967 and thus should be included in whatever autonomous administration is set up.

The PLO Executive Committee yesterday told Qaddafi not to meddle in Palestinian affairs.