Even before Israeli Defense Minister Ezer Weizman warned yesterday that his forces might resume shooting if Palestinian troops in south Lebanon keep firing at them, it was becoming clear that Israel's terms for pulling out of the region it occupied two weeks ago were not close to being met.

The cautious deployment of U.N. forces into the south continued. But even when it is complete, the United Nations will have no control over the Palestinians dug in north of the Litani River.

Last week Weizman said that Israel would begin its withdrawal this Friday. But now it is the unanimous opinion of political and military observers here that the Israelis will have to reduce their objectives or porlong their stay. Most bets are on the latter.

"If they pull out now, it will all be for nothing," a military expert said. "Politically they may want to get out and they are not in a good position to go on leaving those troops in there. But they haven't got what they want."

There is some confusion here about exactly what conditions the Israelis would accept before withdrawing their forces, but virtually none of the terms stated by Israeli leaders or by the government has been achieved.

Palestinian guerrillas remain in control of the port city of Tyre and of the Litani River bridge north of it. Their troops who were driven back to the north side of the Latani inland from Tyre are still within shelling distance of some Israeli towns and settlements, and by all accounts are firing.

No force or combination of forces currently visible is capable of filling the vacuum that would be left if the Israelis pulled out.

An Israeli Cabinet statement last week said Israel wants guarantees that south Lebanon would not serve as a base for "terrorist attacks" into Israel and assurances that civilian inhabitants of the region -- many of whom have cooperated with the Israleis -- would be allowed to live in peace.

It is possible that if the full U.N. contigent of 4,000 men were deployed alongside a proposed brigade of the Lebanese army and the reinforced Christian militias of the south, these conditions could be satisfied. Such an arrangement does not seem likely, observers here say.

Even if it were, the Palestinians would still retain their strongholds around towns north of the river like Nabatiyeh, where there is accumulating evidence that they have been reinforced by as many as a thousand Iraqis.

For many months, ever since they joined Christian militias in the border region in skirmishing against the Palestinians, the Israelis have sought a restoration of Lebanese government control over the area.

The only instrument by which that could be accomplished is the army, which is slowly being rebuilt after it disintegrated during the civil war of 1975-76.

Gen. Victor Khoury, the army commander, is understood to be preparing a mixed-religion brigade of 3,000 men, equipped with tanks and artillery, to leapfrog the Palestinians and try to move into the zone south of the Litani.

Military analysts are deeply skeptical that the Lebanese army is ready to undertake a mission in the field that might bring them into conflict with the well-armed and trained Palestinians.

These doubts are sure to be reinforced by yesterday's announcement that Maj. Saad Haddad, the commander of the Christian troops who have held onto enclaves along the Israeli border since the civil war, was organizing a new army of Christians and Shiite Moslems, complete with conscription, to control the border region.

This poses a ticklish political question because theoretically Haddad and his men are still part of the prewar Lebanese national army -- they have been drawing their pay all along -- and the nature of Lebanese politics is such that it would have caused a storm either to integrate them into the new national force being sent by Khoury or to try to disarm them.

Furthermore, authoritative sources report that at least 300 men from the Christian-held areas of north and central Lebanon have recently entered the south through Israel to reinforce Haddad's troops.

Israel has trained and equipped the Christians along the border in the hope of developing a cordon sanitaire against the Palestinians. It is hard to see how Khoury's army could work side by side with Haddad's to help the Israelis fend off the Palestinians. Without Khoury's army, there is nobody to do it, since the U.N. forces are not there to fight.

The only force that appears capable of curbing the Palestinians is Syria. Experienced observers here are baffled by what appear to be shifts and twists in Syrian policy, complicated by a shakeup in the Syrian government and military that was announced yesterday.

Well-placed sources said that Kamel Asaad, a Shiite Moslem who is speaker of the Lebanese parliament, made an appeal based at least partly on religious grounds to Syrian President Hafez Assad, a member of the minority Alawite sect, last week.

He reportedly asked Assad to send Syrian troops south of their present positions to seize control of Palestinian strongholds at Nabatiyeh and the crusader castle of Beaufort, in order, he said, tospare the Shiite population of south Lebanon any more suffering.

Those positions are north of the litani, beyond the U.N. manadate and beyond the zone seized by Israel, but still close enough that the Palestinians can harass the U.N. forces from there and fire rockets and artillery shells into Israel.

That presumably would stop if the Syrians took over, since Syria does not want to provoke Israel intoa war. Israel has refused ever since the Lebanese civil war to allow the Syrians to move any farther south than they already have.

The Syrians have given indications that they are trying to use their influence to induce the Palestinians to stop shooting, chiefly by threatening to cut off their supplies. So far at least it appears to have had little effect.

Farouk Kaddoumi, the chief diplomatic negotiator for the Palestine Liberaiton Organization, was in Damascus over the weekend for talks with Assad.

In an interview yesterday with Voice of Palestine radio, Kaddoumi said, "Our major objective is to achieve an immediate and unconditional Israeliwithdrawal from the south. It is imperative for us to facilitate all prodecures and measures which might be taken on the Arab and international levels to force this withdrawl."