The Palestinian guerrillas yesterday failed to adopt an agreed overall policy toward the unilateral Israeli cease-fire in southern Lebanon.

One half hour after the truce went into effect, all but small arms fire had ceased, according to reports from the front.

Earlier in the day sporadic fighting, well below the level of the first six days of hostilities, centered around the beleaguered Palestinian-held prot of Tyre.

Bassam Abu Sharif, second-ranking leader in the Marxist-oriented Popular Front for the Liberation of Palestine, vowed that "we will not stop our attacks on the occupying forces until they withdraw from Lebanon."

Spokesmen for the unmbrella Palestine Liberation Organization hedged their position, apparently pending the outcome of high-level discussions how in their third day.

Gen. Ensio Silasvuo, commander of the U.N. Middle East forces, said before the Israeli announcement that "I hope there will be an agreement between us and the Palestinians and that there will be no encroachments."

He was here conferring with the Lebanese government about arrangements for the arrival of a 4,000 man force empowered by a Security Council resolution Sunday to police the cease-fire and monitor Israel's withdrawal.

A first batch of 250 Swedish troops on U.N. duty in the Sinai desert was put on six-hour alert yesterday and was believed headed to Lebanon as the new peacekeeping force's advance party.

Lebanese Prime Minister Selim Hoss spent the day in Damascus conferring with the Syrian leadership about the cease-fire.

Palestinian officials said they were waiting to be approached by the Lebanese, probably after Hoss had come to a common position with the Syrians.

Such roundabout diplomacy was required because the Security Council resolution mentioned the Lebanes government, but not the Palestinian who have been fighting the Israeli.

The wording was apparently dictated by a desire to overcome Israeli reluctance to accept the resolution Mention of the PLO, which Israel refuses to recognize, was sureto have caused problems.

Speaking before the Israelis announced their unilateral cease-fire, a PLO spokesman speculated that theleadership would not want to appear to be the odd-man-out opposing a cease-fire.

"We do not want to be uncooperative," he said. "We do not want to seem obstructive and if the Syrians say "Please cool it" we can do it."

He suggested, however, that even after a formal front-line cease-fire came into effect "we would want to keep up our behind-the-lines operations and might infiltrate more people" into areas occupied by Israel.

He was speaking in the context of guerrilla warfare which the Palestinians hope over the long haul will turn what they expect to be a long-term occupation into a political liability for the Israelis.

In what may have been the last day of fighting, ofur people were killed five miles north of Tyre when their taxi neared the last remaining bridge over the Litani River.

Eyewitnesses said more than 100 artillery rounds landed near the bridge without destroying it.