Israel, alarmed by President Reagan's praise for Saudi Arabia's eight-point Middle East peace plan, has warned that a U.S. move toward embracing even parts of the plan could halt the negotiations on self-rule for the Palestinian inhabitants of Israeli-occupied territories.

Sources said yesterday that the warning, which was couched in diplomatic language, was given to Secretary of State Alexander M. Haig Jr. by Israeli Ambassador Ephraim Evron in a meeting late Friday.

The sources say Evron told Haig that Prime Minister Menachem Begin's government, still deeply concerned by the Senate's refusal last Wednesday to block Reagan's $8.5 billion Saudi aircraft deal, was further upset when Reagan and Haig spoke warmly Thursday about the plan proposed in August by Saudi Crown Prince Fahd.

In a brief exchange with reporters, Reagan, referring to one point in the Fahd plan, said "the most significant part is the fact that they recognized Israel as a nation to be negotiated with." Later that day, Haig said, "There are aspects in the eight-point proposal made by Crown Prince Fahd by which we are encouraged."

The sources said Evron reiterated to Haig that Israel rejects the plan in its entirety. He added that praise for it by the highest-ranking U.S. officials, coming on the heels of the Saudi arms controversy, was likely to increase suspicion within Israel about whether the United States is tilting further toward the Arab side in the Arab-Israeli conflict.

If this suspicion is not put to rest, Evron reportedly said, Begin might find himself under heavy domestic pressure to pull away from the Palestinian autonomy negotiations being conducted with Egypt under U.S. auspices.

That would be a major setback for the administration, which is anxious for progress on the autonomy issue both to further the Middle East peace process and to bolster Egyptian President Hosni Mubarak's efforts to consolidate his control in the wake of Anwar Sadat's assassination.

The sources said Haig agreed that the picture presented in the media of U.S. attitudes toward the Saudi plan could have damaging consequences for the autonomy talks. However, the sources said, Evron, who returned to Israel yesterday for consultations, was given no sign that the administration intends to recant.

The State Department, apparently out of awareness that the situation has caused a new problem for U.S. efforts to reassure the Israelis in the wake of the Senate vote, did try to clarify its position on the Saudi plan even before Haig and Evron met.

In a statement earlier Friday by spokesman Alan Romberg, the department said that "while we welcome certain elements" in Fahd's proposals, "there are other elements with which we have problems."

Fahd's eight points, as published in Arabic in Saudi publications, call for Israeli withdrawal from all Arab territories, including Jerusalem occupied in 1967; removal of Israeli settlements from these territories; freedom of worship for all religions in Jerusalem; recognition of the right of the Palestinians to return to their homeland in what is now Israel; establishment of a transition period, under U.N. mandate, in the West Bank and Gaza Strip; establishment of a Palestinian state with East Jerusalem as its capital; affirmation of the right of all countries to live in peace, and a guarantee of these principles by the United Nations or some of its members.

The last point is what drew Reagan's praise. However, translations from the Arabic have left unclear whether Fahd meant the "people" or the "states" of the region, a distinction that makes a big difference as to whether Saudi Arabia is disposed to accept the legitimacy of Israel.

As Reagan's statement made clear, the administration has chosen to interpret it as a conditional offer by the Saudis eventually to recognize Israel. Romberg described the plan as reaffirming support for U.N. Security Council resolution 242, which calls for recognition of the right of all Middle East states to live in peace.But the Saudis have never explicitly accepted 242.

The upshot is to leave in confusion whether the praise by Reagan and Haig foreshadows an intention to try and merge elements of the Saudi plan into the Camp David process or whether they were trying to bolster administration arguments that the Saudis are moving toward a moderate stance in the Arab-Israeli conflict.