The Syrian missile crisis, the Israeli bombing of Baghdad and Beirut and the fragile new "cease-fire" between the Palestine Liberation Organization and Israel across the Lebanese border have sharpened Ronald Reagan's focus on the Middle East.

But nothing is likely to do more to influence his thinking -- or the course of American policy -- than the consciousness-raising he will undergo this week at the hands of a master: Egypt's shrewd, mercurial, impassioned, larger-than-life president, Anwar Sadat, whose visit to Washington begins tomorrow.

The hero of the Jerusalem breakthrough will be prepared to make the president anoffer he may be hard-put to refuse. Sadat will present himself as Mr. Strategic Consensus, even more acutely sensitive to the Soviet menace than the president himself. His list of worries will run from the Persian Gulf across North Africa and southward to Namibia.

He will point to the Soviet "arsenal" in Ethiopia, the Libyan move into Chad, threats to Tunisia and the Sudan -- all in support of a pitch for sustained American economic aid (over $1 billion a year) and increased military aid (more F16 aircraft, tanks, etc.).

An offer of Egyptian bases for American use, under the most generous terms, will be reaffirmed. "On strategic consensus," says one Egyptian official, "there is a complete commonality of views." But the price for Secretary of State Alexander Haig's "strategic consensus" against the Soviets has to be some demonstrable progress in the Camp David "peace process" to resolve the Arab-Israeli conflict. This means resumption of the autonomy talks to provide self-determination for the Palestinians on the West Bank and Gaza.

It also means (and here's the hard part) firm American pressure to bring an end to what Sadat and other Arabs regard as calculated Israeli obstruction of that critical second part of the Camp David Framework that had to do with the Palestinians. (The first part, well on its way to completion, had to do with Israeli withdrawal from the Sinai, and the already-concluded Israeli-Egyptian peace treaty.)

At the State Department, the linkageis accepted. At the White House -- well, it was not too long ago that a European foreign minister raised with Reagan the question of the "Palestinian problem" and was plunged into despair by his response:

There is no "Palestinian problem," the president is said to have replied -- it's a matter of "Arab refugees" who ought to have been assimilated by the Arab world years ago.He was principally concerned at the time with forging some sort of common front between such unlikely collaborators as Israel, Egypt and Saudi Arabia against Soviet encroachment.

How far the president may have developed his thinking is hard to tell. What with one thing or another -- taxcutting, the budget, Ottawa -- he has been preoccupied. The old actor, they say, likes to take one part at a time. But now the Middle East is inescapably crowding in, with a heavy schedule of further visits by the heavies of the area (Israel's Menachem Begin, Jordan's King Hussein and, later in the fall, the Saudi Arabians).

And in the view of many authorities -- Sadat included -- a confluence of events may just conceivably have opened up one of those fleeting opportunities for Middle East peacemaking which, if missed, will be a long time returning.

That will be Sadat's most important message. Merely by acknowledging a cease-fire, Israel and the PLO have significantly acknowledged each other. A more forthcoming mutual acceptance is a pre-condition, in Sadat's mind, to any Palestinian settlement.

In the Lebanese crisis, a substantial Saudi Arabian role behind the scenes has finally caught that crucial country up in the peace process. That the Syrians would even talk to Reagan's special envoy, Philip Habib, is seen by the Egyptians as evidence of some moderation. Iraq's relative restraint over the loss of its nuclear reactor is similarly viewed as a hopeful portent.

Menachem Begin's capacity to deepend and expand his West Bank occupation at the expense of eventual "autonomy" is, in one sense, intact. But his hand is weaker, and his susceptibility toAmerican pressure enlarged, by his diminished political support from the American public, in Congress, within the American Jewish community. Or so Sadat is said to believe.

"The time has never been riper," says one Egyptian authority. It will become measurably less so if there is no Palestinian progres and the scheduled Israeli withdrawal from the Sinai by next spring begins to make Camp David look in Arab eyes more and more like a self-serving Egyptian "separate peace" with Israel.

If this forces Sadat to se a need to work his way back into the good graces of his Arab brothers, the form this would likely take would not help consolidate the "strategic consensus" so dear to Haig and Reagan. That's a point Sadat will not hesitate to make this week.