Egypt unexpectedly brought the disputed effort to amend U.N. Security Council Resolution 242 into the Palestinian autonomy talks today, angering Israel, and raising an unforeseen threat to the future of the negotiations.

Justice Minister Shmuel Tamir, an important member of the Israeli negotiating team, said the Egyptian move "created a shift on a central issue which will obligate Israel to reexamine all the factors."

The chief negotiator, Interior Minister Josef Burg, was quoted by the government-run Israeli radio as saying Israel would review its obligations under the peace treaty to participate in the talks if the key U.N. resolution is changed, as endorsed by Egypt.

Taken together, the statements were seen as an indirect threat to reconsider participation in the autonomy talks, now in their fifth plenary session, if the moves underway at U.N. headquarters among U.S. and Arab diplomats produce a substantial amendment to the 12-year-old resolution that is the basis of Middle East peace efforts.

Israeli spokesman Dan Pattir said that after "clarifications" at a meeting between the Egyptian and Israeli chief negotiators, the current talks would continue through their third day Tuesday. But he reinforced the impression that Israel could suspend its role if the resolution is finally amended, saying:

"Israel will not agree to or accept under any circumstances any change in 242. This is the only basis on which negotiations can be conducted."

Since its passage in 1967, Resolution 242 has been regarded as a departure point for any efforts toward a Middle East settlement. It mentions the Palestinians only as refugees and the PLO has never accepted it. Now, the ;the United States is searching for a revised formula and there have been indications that the Palestinian leaders may be shifting their position.

It was reported here that the Israeli Cabinet also had warned the Carter administration, in a message relayed by the Israeli ambassador yesterday, that it would reconsider its treaty commitments on the talks if the resolution were altered.

[U.S. officials said in Washington that Secretary of State Cyrus Vance telephoned Israeli Ambassador Ephraim Evron today in an effort to smooth over relations. They also reported that Evron had lunch with Assistant Secretary of State Harold Saunders after speaking with Vance. No details of either discussion were immediately available.]

The Israeli outrage reflected a strong desire to keep the dispute over the amendment proposal separate from the talks here on setting up self-rule for Palestinians in Gaza and the West Bank. It also was a measure of the extreme sensitivity here to any suggestion that involves linking, even indirectly, the Palestine Liberation Organization and the autonomy talks.

Prime Minister Mustafa Khalil, Egypt's chief negotiator, touched off the dispute in the closing minutes of today's second negotiating session. Egypt endorses a balanced amendment to Security Council Resolution 242, he said, because this could bring into the negotiations the Palestinians, Israeli officials, explaining their determination to prevent its amendment, said the resolution also underpins the Egyptian-Israeli peace treaty of March 26, and that to change it now would rob the treaty of one of its foundations.

Running through their explanations was fear that the United States could be moving away from its refusal to deal with the PLO and reassessing its stand on Palestinian claims to a homeland.

Before Khalil's remarks on the amendment drive, the talks centered on efforts to arrange elections on the West Bank, conference sources said. An Egyptian suggestion that Egypt, Israel and the United States send tripartite observer teams to supervise the voting as well received and Israeli sources said it had a good chance of winning approval.

The Egyptian insistence on allowing political parties to function freely in the West Bank and Gaza met with hostility, however, and Israeli negotiators vowed that pro-PLO political groups will never be tolerated, the sources said.

who are the main subject matter.

To the Israelis, however, the Khalil declaration seemed the latest of a series of developments they regard as damaging to their position. In addition, reports that the United States is cooperating in the moves to amend Resolution 242 have troubled the Israelis even more.

The proposed amendment would add to the resolution a reference to Palestinian rights or to the right to a homeland. This, proponents say, would prompt the PLO to accept the resolution, which would be tantamount to recognizing Israel and its right to exist.

This, in turn, would pave the way for a dialogue between the PLO and the United States in the hope of winning # at least tacit PLO approval of participation by West Bank Palestinians in the self-governing authority the negotiations are intended to set up.

Without PLO approval, U.S. diplomats fear, West Bank leaders will continue to boycott the talks and make a sham of whatever self-rule system is set up in elections scheduled for next year. CAPTION: Picture, MUSTAFA KHALIL...pushing for amendment