The Christmas summit between Egypt and Israel has failed to produce a sudden break-through toward peace in keeping with the dizzying pace of recent events. But the negotiating process remains very much alive, and with it the chance for compromises and achievements.

Perhaps it was inevitable that the world's soaring hopes sent aloft in large degree by the participants themselves, would come to earth when the tough issues were confronted. The impact, while jarring, was not a crash. The opinion among many diplomats, as least, was that the return to reality need not to prove to be disabling.

The most serious question is whether President Anwar Sadat and Prime Minister Menahem Begin can sustain the popular and polititcal backing for important steps in the face of increased disappointment and disagreement their home constituencies.

As [WORD ILLEGIBLE] sets in, so does controversy. [WORD ILLEGIBLE] main asset of Sadat's "television shock diplomacy" was its ability to overwhelm the critics and to mobilize an outpouring of public support.

The Egyptian leader suggested to reporters today that he will seek to mobilize world opinion behind his drive for more Israeli compromises. The Israelis are not novices at the mobilization of opinion, however. A new drive based on details rather than hopes and dreams may be more difficult than Sadat's initial forays.

Sadat and Begin did not seek to disguise their agreement over the key issue of the West Bank and the Palestinian question in this morning's news conference in Ismailia. By placing the issue on the line in public, pressures for compromise as well as counterpressures against compromise will be generated in Israel. Egypt and elsewhere in the Arab world.

A fact of great importance is that Sadat refused to buy a vague resolution of the Palestinian question. Thus he showed his determination, at this stag, not to make the "separate peace" with Israel which is the hope of many in the Jewish state and the fear of many in the Arab world.

Informed sources said Begin was willing to describe his proposals for Palestinian "self-rule" as "interim" arrangements without stating what the final deal would be. The Israelis had hoped Sadat would accept this delicate ambiguity, but the Egyptian leader held out for better terms.

What might settle for in the end is another question. Some close observers of the negotiations believe the Egyptian president will be flexible on details if he can stand behind general principles of Palestinia self-determination. His press conference answers today suggested anew that Sadat is drawing a sharp distinction between "the Palestinians" and the Palestine Liberation Organization.He seems to have little use at the moment for the PLO.

Israeli withdrawal from nearly all of the occupied Sinai appears to be Sadat's for the asking, a prospect that must be extremely tempting to the Egyptian president. But he said again "Sinai deal" in the Kissinger mold but rather a comprehensive Arab-Israeli agreement.

The Egyptian people, whose outpouring of peace sentiment has surprised even Sadat, are weary of sacrifice and deprivation. One U.S. estimate is that as many as 90 per cent of them would be willing to settle grudgingly for a "Sinai only" deal with Israel if it would seem to offer peace.

Sadat would lose his standing in the Arab world if he were to accept a separate peace, and he might well lose his Saudi and other Persian Gulf financing. The United States is also strongly opposed to a separate Israel Egypt arrangement.

The newly formed defense commitee headed by Egyptian War Minister Mohammed Ghani Gamassi and Israeli Defense Minister Ezer Weizman will not doubt concentrate beginning next month on the Sinai. Thus Cairo will continue to hold the seeds of a separate Sinai-only pact.

The political committee headed by Egyptian Foreign Minister Mohammed Ibrahim Kamal and Israeli Foreign Minister Moshe Dayan will concentrate on the West Bank issue, with the United States and United Nations furnishing observers. These talks, in Jerusalem, will center on the possibility of a comprehensive settlement.

The balance of the two possibilities is likely to continue to hold the attention of the diplomats and the watching world. It is certainly true, as Begin and Sadat declared, that they have come to a great turning point. It is not yet clear which way their talks - and the Middle East - will turn in the the months ahead.