After a week of marathon negotiations intended to revive the dormant Middle East peace talks, U.S. Ambassador-at-large Alfred Atherton Jr. today extended his visit to Israel with no significant breakthrough reported by either side.

Atherton, who had been scheduled to go to Cairo today to present to the Egyptians Israel's position on two disputed clauses in the compromise draft peace treaty, asked for further meetings.

In Washington, the State Department said Atherton will stay in Jerusalem until he has a "full understanding" of Israel's position.

The Israeli-American negotiations, which began last Tuesday with muted expectations voiced by both sides, were described by Israeli and U.S. sources as progressing steadily but slowly, with some flexibility demonstrated by the Israeli team on the issue of whether Egypt will be entitled to a mandatory review of Sinai security arrangements five years after the signing of a treaty.

Eliahu Ben-Elissar, director general of the prime minister's office and head of the Israeli negotiating team, when asked if the discussions had reached a critical stage, replied, "There is no critical stage... It is, well, a cruising speed."

The discussions, although shrouded in secrecy by both sides in an attempt to avoid a political debate in the open before Atherton goes to Cairo, are said to have focused not on the substantive issues of the draft treaty text, but instead on interpretative notes that are to be attached to the pact to clarify two key clauses.

The clauses deal with Egypt's demand for a review of the Sinai security arrangements after five years and with Egypt's attempt to soften a treaty provision assuring that the pact would supersede mutual defense agreements between Egypt and other Arab states.

Israel is demanding that the proposed interpretative note make clear that Egypt would be entitled to aid another Arab state in war only if the cause of the war was an unprovoked act of Israeli aggression. The dispute so far, sources said, has been over the definition of an "unprovoked act of aggression," and the Israeli Cabinet is said to have concluded in a classified debate yesterday that not much headway is likely on the issue at this level.

Major political issues, such as Egypt's demands for a fixed timetable for implementation of autonomy for West Bank and Gaza Strip Palestinians, have not been negotiated during the Atherton talks, Israeli sources said.

Atherton and State Department legal adviser Herbert Hansell have been meeting with a legal team headed by Ben-Elissar and including Israeli Foreign Ministry legal adviser Meir Rosenne, Attorney General Yitzhak Zamir and international law expert Ruth Lapidot.

News services reported these other Middle East developments:

King Hussein of Jordan began a two-day visit to Saudi Arabia. Jordanian officials said he would discuss the Arab-Israeli conflict and other issues with King Khalid.

Former president Ford toured the holy sites of Jerusalem after breakfast with Israeli Foreign Minister Moshe Dayan. Ford also asked to visit the grave of former prime minister Golda Meir.

Lebanese officials in Beirut said at least three persons were killed and several wounded when Israeli gunners shelled the southern town of Babatiyeh. Israeli officials said the shelling was by Christian militia.