Logic says it's the Arabs' move. Syria has no further excuse for its continued presence in Lebanon if it is invited out.

Jordan's King Hussein, having resisted participation in the Reagan "initiative," in part for lack of evidence that the United States has any influence on Israel, now has that evidence in Secretary of State George Shultz's role in the Lebanese/Israeli withdrawal agreement. The same may be said for the so-called Arab moderates (Egypt, Saudi Arabia) who applied the same test.

So the way should soon be opened for renewed efforts to crack the larger Arab-Israeli case, right?

Absolutely, if you believe in the Tooth Fairy--and in logic as a prime mover in these matters. But even assuming that the initial Syrian rejection of the Lebanese-Israeli withdrawal agreements is a blowhard opening gambit, the terms of the Israeli pullout give Syria ample scope for killing time by spinning out negotiations on its own withdrawal terms.

And at this crucial stage, time is everything. That's why the celebrated Shultz breakthrough in Lebanon may be not so much a "milestone" as a millstone--a real drag on progress along the Reagan administration's chosen path to a wider Arab-Israeli settlement.

That's not to knock Shultz's effort. Without it, there would be no hope of cooling off the Israeli-Syrian confrontation in Lebanon and of hastening the day of Lebanon's return to some measure of sovereign control over its territory.

Now there is at least a chance of achieving that much. But the longer it takes, the more time Israel will have to settle the question of the West Bank by de facto Israeli annexation under the current crash program of building permanent, city-style Jewish settlements--to foreclose Ronald Reagan's stated preference for a West Bank linked in federation to Jordan.

With the benefit of hindsight, many experts will tell you this might not have been the case last fall. That was before the Soviets had gotten fully embarked on rebuilding Syria's armed forces and adding sophisticated new weaponry, and before King Hussein had first edged close to a partnership in the Reagan "initiative," and then backed abruptly away. The Reagan administration might even have seized an opportunity then to try to pry a weakened Syria from Soviet influence by including in its presumably comprehensive peace plan some note of Syria's claim to the Israeli-occupied Golan Heights.

But sidling up to any regime as radical and Soviet-connected as that of Syria's President Hafez Assad goes squarely against the ideological grain of the Reagan administration. Its focus was on Lebanon, and on winning the favor of the Arab "moderates" by addressing their concerns over the Palestinians and the West Bank.

Not even the latter effort, launched with great fanfare on Sept. 1 of last year, had much show of steam behind it. Reading the weak signals, the Israelis hung tough, buying time while proliferating their West Bank presence. Only after Hussein buckled to pressure from the Palestine Liberation Organization and effectively removed the threat ("mortal" to Israel, according to Menachem Begin) of the Reagan "initiative" did the Israeli government find it safe to accept Lebanese withdrawal terms well short of its initial demands.

On the face of it, this puts the monkey on Syria's back. But the Syrians, sharing Israel's distaste for the Reagan "initiative," can be counted on to play Israel's game. There is plenty for the Syrians and the Lebanese to bargain about--and reports suggest that more is being added by new Syrian troop movements into Lebanon and a serious "leakage" of returning PLO guerrillas as well. The Syrians can spin things out merely by insistence on a residual Syrian presence comparable to the revisiting rights and other security concessions granted to Israel.

The Syrian game fits the Soviets' spoiler role, by working against the U.S. peace effort and a consequent widening of U.S. influence in the Mideast. The Israelis, meanwhile, can take out insurance against an accidental outbreak of hostilities with Syria and also lower their casualties at the hands of scattered guerrillas by a partial, unilateral pullback to more defensible areas.

Ultimately, there may be liberation for Lebanon. But by then, the Reagan "initiative" will be dead. And all the tensions and conflicts that threaten the region's stability and have brought five wars in 35 years will still be very much alive.