ISRAEL, EAGER to end casualties and to put a bad war behind it, had wanted to negotiate its way out of Lebanon. But the Lebanese government, powerless and bound by Syrian high strategy, has made that impossible for now. It is not clear whether the Israelis will return to Nagura in January for another round in their United Nations-sponsored withdrawal talks. The signs are, however, that they realize negotiations are not promising and that they must tackle these decisions on their own.

Broadly speaking, the Israelis have three choices. One is doing nothing, but the casualties and other costs make this impossible. A second -- a full unilateral withdrawal -- is beyond the capacity of a government that includes as an equal partner a party, Yitzhak Shamir's Likud, unready and unwilling to write off its war. That leaves the third: a partial withdrawal, which is what Prime Minister Shimon Peres of Labor and his defense minister, Laborite Yitzhak Rabin, are plainly committed to. A Cabinet decision is expected before very long. If it is not forthcoming, it will mean that Mr. Peres has defaulted on one of two leading campaign promises (the other was to repair the economy), and it will be hard to see why he deserves to remain prime minister.

Why did the Syrians insist that the Lebanese government stick to the laughable demand that Israel turn over to the Lebanese army, a puppy dog, all of southern Lebanon down to the Israeli border? Syria calls all the shots in Lebanon and does not explain its reasons. In any event, Damascus remains responsible, in fact if not in name, for what happens in the parts of Lebanon that Israeli forces evacuate. The expectation is that Syrians and Israelis will set up a new series of "red lines" indicating their common intent to treat Lebanon as a buffer between them and to avoid menacing each other's vital security interests. As usual, it falls to American diplomacy to be the go-between.

The withdrawal now being contemplated excludes eastern Lebanon, where an informal "red line" already ensures that Israeli and Syrian forces very near each other remain tightly controlled. The main withdrawal will affect southern Lebanon between the mountains and the sea. It will liberate most of Israel's current Shia tormenters. It will be up to the Shias, and to U.S. peacekeepers also in the area, to take over the role the Israelis have played of dampening intra-Lebanese strife and blocking the return of Palestinian gunmen. As a practical matter, the effective performance of these tasks could make possible early Israeli evacuation from the last piece of southern Lebanon.