Confronted with growing signs of deadlock in Egyptian-Israeli peace negotiations, President Carter warned the two countries yesterday that the United States will demand that they live up to the generalized Camp David accords even if they cannot agree to sign a formal peace treaty.

Meeting with reporters shortly before he opened talks with Egyptian Vice President Hosni Mobarak, Carter for the first time proposed that "in a few cases it might be necessary to modify the Camp David accords if both sides agree" in order to overcome the negotiating problems that have stretched the talks here into their fifth week.

Carter did not specify what "cases" he had in mind, but he simultaneously offered reassurances that the changes would have to be mutually acceptable and a warning that "if both sides don't agree, then our adamant position would be that the Camp David accords can't be abrogated, because this is just as solemn an agreement between these two antions as a future peace treaty will be."

Reports of new proposal brought to Washington by Mobarak containing specific timetables for future Arab-Israeli negotiations have upset the Israelis, who view them as falling outside of the Camp David agreements and who appear ready to reject the new Egyptian ideas.

While senior officials from each of the three countries continued to say that they thought Egypt and Israel would eventually sign the peace treaty that was outlined at the Camp David summit, the negotiating conflict appeared to deepen yesterday.

In Washington, Osama al-Baz, one of the most important members of the Egyptian negotiating team, said that Egypt would insist on specific timetables for setting up Palestinian local governing councils in the Gaza Strip and the West Bank, and on an Egyptian presence in Gaza to oversee the elections for the councils.

"You have to have a certain date people can look toward, and not become frustrated and vulnerable to radical pressures," al-Braz said in a telephone interview. "We are not seeking a cosmetic solution, but something concrete."

In Jeusalem, however, Foreign Minister Moshe Dayan was quoted as having in effect rejected both the Egyptian demands for timetables and an American compromise proposal, which would have put off the deadline for West Bank and Gaza elections until Dec. 31 next year.

"Israel cannot commit itself to any date," Dayan told members of the security and foreign affairs committee of the Israeli Parliament, Radio Israel reported.

But Dayan also said that the text of the peace treaty was nearly complete. Defense Minister Ezer Wiezman said just before leaving Washington to return home for Sunday's crucial cabinet debate on the treaty that the new Egyptian proposals "should not be stumbling blocks" to finishing the treaty.

Weizman spent two hours with the Egyptian vice president yesterday after Mobarak and Carter concluded their 90-minute meeting. Both conversations were reportedly devoted to the complex set of proposals the Egyptians have brought forward and which appear to raise the question of "modifications" that Carter referred to at a breakfast meeting with White House reporters.

The conflict continues to center on Israel's refusal thus far to agree to any formal linkage of the treaty to the long-term Arab-Israeli negotiations set out in the separate Camp Gaza and on Egyptian President Anwar Sadat's increasingly specific proposals for timetables for the second set of negotiations.

The Carter administration sought over the weekend to bridge those differences by proposing that the two nations agree, in a letter accompluing the treaty, to commit themselves to open negotiations one month after the treaty was signed in order to set up elections for the Palestinian councils before Dec. 31, 1979.

But Sadat surprised Jerusalem and Washington by deciding to send Mobarak to Washington with new proposals before the Israeli cabinet had even taken up the U.S. compromised idea, which was given to Israeli Prime Minister Menachem Begin on Sunday.

With confusion mounting and charges of bad faith beginning to creep into the negotiations, al-Baz and other conference souces yesterday gave detailed descriptions of the new Egyptian proposal, which the Egyptian diplomat insisted are intended to make it easier for both sides to sign the treaty.

Egypt now wants Israeli agreement - either written or verbal - that Israeli military withdrawal from the Sinai peninsula will be closely tied to the holding to elections and the setting up of administrative councils in the Gaza Strip.

This would have the practice effect of moving the elections in the Gaza Strip to September 1979 if the peace treaty is signed by Dec. 17 and Israeli withdrawal is completed within nine months as prescribed by the Camp David agreements.

Establishing an "Egyptian presence" in the tiny enclave, inhabited by 400,000 Palestinians and administered by Egypt until the 1967 Israeli occupation, at the time of the elections "would prevent a vacuum forming" in Gaza at a critical time, al-Baz noted.

He indicated that the Egyptians were prepared to accept one timetable for the Gaza and West Bank territories that would call for holding elections by the end of next year.

At his meeting with reporters, Carter voiced a sense of frustration and disappointment over the changes in negotiating positions by both sides and over public discussion of those positions.

"I anticipated after Camp David that in just a few days the agreement could be reached," he said, adding remarks on modifications that seemed to bring him closer to the Egyptian position than to that of Israeli officials who have suggested that Begin politically cannot afford to have the original accords reopened for discussion.

"Camp David, even though it was quite substantive - the text was quite substantive - had to be embellished or elaborated with specific time schedules, exact drawing of lines" and many other items, he said.

Asked if another Camp David-type summit might be needed to break the deadlock, the president replied: "I really hope not. This is not something we are contemplating . . . And I hope and pray and expect that it will not be necessary.