It was good to hear Secretary of State George Shultz say the Palestinians must be brought into the political act in the Middle East, and it was good to hear him lay out the broad terms on which they must be brought in. If a total collapse can yet be avoided in Beirut, then the Palestinian issue, now moving hesitantly to the edge of official American concern, may move toward the center. But for good to come of it, the move must be made with care.

I wave this warning flag for a reason. As never before, events have positioned the Palestinian issue for joint political address --though, to be sure, the key parties diverge sharply on how to address it. No matter how the Beirut siege plays out, the PLO will have been converted by Israeli arms and Arab (and Soviet) abandonment from a military threat to an organization with only a political option left.

I suspect that the bloodiness of Israel's conduct in Lebanon has been exaggerated, but, real and imagined, it has given an extra latitude to an American policy on the Palestinians that would not be as deferential to Jerusalem as in the past. This has happened, moreover, as a secretary of state takes office who sees a new urgency in the Palestinian issue.

It would be wrong, however, to exaggerate the ripeness of the situation. Excessive anxiety could make the Israelis and their friends more rigid, as excessive overconfidence could cause the Palestinians and their friends to overreach. For the United States--on this issue, now, again--to raise expectations on which it did not deliver would be to invite a policy disaster.

The immediate focus lies in Beirut: how to save the city from the ruin which the Palestinians and Israelis, twins in cynicism, threaten to bring upon it by holding out and by coming in, respectively. The PLO is now suggesting it will swap evacuation for American recognition. That is, if the United States will drop its condition for dealing with the PLO--that the PLO first formally accept Israel--then the PLO will allow Beirut to be saved.

To which a reasonable American ought to say: no thanks. The PLO demand is more than nervy. It is blackmail for the PLO to hold a pistol to Beirut's temple and demand that the United States make an unearned political gift that would violate a solemn commitment. Nothing could sooner convince Israelis that the United States means to sell them out. Nothing could better thwart progress on the only front where a settlement can ever be made--in direct negotiations between Israelis and Palestinians.

It is illuminating to see what a premium the PLO leadership places on a breakthrough to Washington. Obviously, a breakthrough would be of incalculable help to the Palestinians in achieving their legitimate political aims--by which I mean self-determination within borders and under conditions negotiated with the Israelis. It is right that Palestinians should have full American help in pursuing these aims.

But they should have help on American terms, and American terms are the reasonable and principled ones stated in 1975 and restated in timely fashion this week by Shultz at his confirmation hearing. The PLO, he said, should abandon terrorism, accept Israel as a sovereign state and negotiate a settlement on the basis of the Camp David accords.

That would be a stiff price for the PLO and would doubtless cause splits and deep recriminations in the organization. Understandably, the PLO would like to buy in cheaper. To that end, the organization is now circulating a new set of words that hint at acceptance of the American terms. But they only hint. The PLO's position remains fuzzy and repudiable. The PLO needs to be encouraged to move along further.

Those who support its legitimate political purposes--I do--do it no service by indulging its inclination to fudge. This is what Sen. Charles Percy did with his statement that an unidentified "high-level friend of the U.S." had confirmed the PLO's readiness to recognize Israel's right to exist. Let us hear it straight from Yasser Arafat.

Will the PLO bite the bullet? The reasons why it may not are plain enough. The reasons why need to be underlined. By accepting Israel without funny business, the PLO would put the United States under a profound obligation to help produce a political result that the PLO is manifestly unable to produce in any other way--now less than ever. The PLO would also, I believe, trigger the transformation of Israeli attitudes that, when Egypt did it, brought Egypt all its lost territory and peace..