Egyptian President Anwar Sadat, in his first hint of concern, warned President-elect Ronald Reagan yesterday that his plans for a harder-line U.S. foreign policy should not penalize Egypt or else "he will lose us."

Sadat's comment, in an interview distributed by Egypt's official Middle East News Agency, appeared to grow from fears reported in Cairo that the Reagan administration could allow Egyptian concerns -- particularly the Palestinian autonomy talks -- to be overshadowed by its desire to reassert American national interests overseas.

"I want to tell the American people at this moment in particular that when they urge President Reagan to follow a hard-line policy toward the Soviet Union, they should not include America's friends in this policy," Sadat said, according to the news agency's Arabic-language version of an interview with an American correspondent.

"For if he follows a Hard-line policy toward us, he will lose us and lose our feelings. The American people should tell Reagan that we are sincere friends . . . and, therefore, we except the other side to be sincere with us and to respect our pride and national ambitions."

It was not clear whether Sadat was responding to any specific signal from the incoming Reagan administration. There has been speculation, however, that the new president will put less emphasis on the Camp David process and autonomy talks and more on protecting access to Persian Gulf oil from any Soviet threat.

Largely for that reason, Egyptian officials during the U.S. election campaign made little secret of their preference for President Carter. On one hand, they felt that in Carter they had a tried friend. On the other, they privately expressed concern that Reagan could view Israel as such a valuable strategic ally against Soviet influence that he would be reluctant to pressure Jerusalem for concessions in other areas, such as the long-stalled autonomy talks.

This would be a major setback for Sadat, who has based much of his planning on U.S. ability to influence Israel to make the accommodations necessary for even relative success in the autonomy negotiations. Highlighting this strategy. Sadat reiterated his call for a three-way summit with Prime Minister Menachem Begin of Israel, himself and the U.S. president to bring the talks out of their stall.

"Without the United States, peace cannot prevail in the Middle East and the problems of the region cannot be solved," he said.

"But let us give the president-elect enough time to prepare himself before joining us," he added.

Sadat is known to feel that in any case little progress is likely in the autonomy talks while Begin remains prime minister. Consequently, he is said to be prepared for a pause until the Israeli elections, scheduled for next fall at the latest.

The Egyptian leader coupled his warning to Reagan with a pledge that "we will open our hearts and take 10 steps in its direction" if the United States under the new administration treats Egypt as a friend.

"Let us be friends and let our cordial feelings be with you," he said, "and you will get even more of these cordial feelings and you will find us a friend at the time of need."

Sadat already has made Egyptian military bases available for U.S. use. His troops currently are involved in joint exercises in the Egyptian desert designed to test the Carter administration's Rapid Deployment Force, and it was against this background that he warned against a shift in U.S. policy away from reliance on Egypt as a strategic partner.

As an example of what not to do, Sadat cited the policies of the late president Lyndon Johnson and the late secretary of state John Foster Dulles, who, he said, "treated the good Egyptian people with contempt because we refused to be agents of the United States."

In other Middle East developments:

Sadat told the Egyptian parliament that he is still willing to provide Israel up to a million cubic meters of water from the Nile River "for the sake of a solution to the Palestinian problem and Jerusalem." Sadat first made the offer to Begin in May 1979, when it was turned down.

Syria sought to organize support for its boycott of an Arab summit conference scheduled to begin Tuesday in Amman, Jordan. Among Syria's allies in the Steadfastness Front, only South Yemen has announced it will not attend. Libya, Algeria and the Palestine Liberation Organization, the other front members, have not announced their decision. The PLO, however, has urged postponement, and PLO leader Yasser Arafat lobbied for delay in several gulf capitals.

Begin's Herut Party secretariat expelled former Israeli defense minister Ezer Weizman for voting against the prime minister's Likud coalition in last week's no-confidence motion, Radio Israel reported. Weizman announced Friday his intention to form a new party to run against the Likud and the opposition Labor Party in Israel's upcoming elections.