President Carter said yesterday the Camp David Middle East peace talks may be elevated "later this week" to a new summit meeting that will include himself and Israeli Prime Minister Menachem Begin but not Egyptian President Anwar Sadat.

Egypt would be represented by Prime Minister Mustafa Khalil. He had been closeted at Camp David the past five days with Secretary of State Cyrus R. Vance and Israeli Foreign Minister Moshe Dayan in the latest U.S.-mediated effort to break the deadlock blocking an Egyptian-Israeli peace treaty.

After a 45-minute meeting at the White House yesterday with the three negotiators, Carter appeared before reporters to read a brief statement. He said in part:

"In the light of the developments in the talks at Camp David this past week, we are discussing with the two governments the possibility of moving these negotiations to the head-of-government level later this week. Prime Minister dBegin would then represent Israel and Prime Minister Khalil, who has been authorized by President Sadat to conclude the negotiations on behalf of Egypt, would represent Egypt."

Carter added: "I am prepared to spare no effort in achieving the peace settlement foreseen in the Camp David accords reached last year. The other two partners in these negotiations share this determination."

Following the White House meeting, Dayan and Khalil left Washington for consultations with their governments. White House press secretary Jody Powell said later that "we ought to know about midweek" if these latest developments in the Middle East peace process will result in a second Camp David summit.

For the moment, though, there was confusion about whether the newest twist in the negotiations means there is a real possibility of a breakthrough toward the peace treaty agreed to in principle by Begin and Sadat under Carter's mediation at Camp David last September.

Negotiations on the actual treaty began here in October but then bogged down in a number of disagreements. Several U.S. efforts including a Middle East shuttle mission by Vance in December failed to get the talks moving again, and both Egypt and Israel since have made no secret of their belief that the outstanding issues can only be resolved at another summit.

Until now, though, Carter had been unwilling to take that route. Instead, he decided to have Vance hold another round of ministerial-level talks first to explore whether there was sufficient flexibility on both sides to give a new summit a reasonable chance of success.

All the parties involved refused yesterday to comment on what happened at Camp David during the latest round. It was understood that, while serious differences remain, both Egypt and Israel showed the signs of flexibility sought by the president.

In addition, concern about the uncertainties that the turmoil in Iran pose for the entire Middle East is believed to have convinced all three governments that failure to reach agreement quickly could doom hopes for a peace treaty.

These factors are understood to have produced agreement among the ministers at Camp David that an attempt should now be made for a package settlement of all unresolved differences and that such an effort, to be successful, requires the direct participation of each country's top decision maker.

In the light of that decision, there was considerable confusion last night about why Sadat would not attend the proposed summit. That factor even caused speculation that Carter regards Israel as the more recalcitrant negotiating partner at this stage of the talks and wants Begin here to put pressure on him.

It has been made clear, however, that Khalil, whose authority in the Egyptian government is second only to Sadat's, has been give the necessary power to negotiate on fully equal terms with Begin and Carter. On the Israeli side, by contrast, Dayan repeatedly has stressed that only Begin can speak with the full authority of the Israeli government.

The principal unresolved issue in the talks involves Egypt's insistence that the peace treaty be accompanied by a so-called "side letter" spelling out a timetable and target date for completing separate negotiations on establishing Palestinian autonomy in the Israeli-occupied West Bank and Gaza Strip.

Sadat wants this linkage to protect himself against charges in the Arab world that he is foresaking the interests of the Palestinians in order to achieve a separate peace with Israel. The Israelis, while saying they are willing to negotiate the autonomy issue as soon as a peace treaty is signed, so far have refused to accept a timetable or target completion date.

Other major sticking points involve disagreements about provisions for reopening the treaty to revision in the future and questions of its relationship to other treaty obligations of the two countries. Egypt has refused to agree to an article in the draft text giving the treaty primacy over Egypt's mutual defense pacts with other Arab nations that might come into conflict with Israel.

Even if Egypt and Israel agree to the new summit, there are questions about whether it can begin this week as Carter said. In addition to all the logistical preparation that would be required, Carter is scheduled to make a two-day visit to California beginning Friday.

In response to questions about that, Powell said that matters of timing would be addressed and sorted out once it becomes clear whether there is going to be a new summit at Camp David.