No official or guerrilla interviewed at the makeshift Palestine Liberation Organization military headquarters in this isolated northern Lebanese port city today disputed the fact that the PLO is grossly outmanned and outmatched in its battle with rebels backed by crack Syrian troops and tanks.

But official spokesmen and loyalist PLO guerrillas pledged to continue to fight in the eastern Lebanese Bekaa Valley 35 miles south, firing on Syrian troops if that becomes necessary to defend themselves. They conceded that in the end they could lose but they saw a need to resist that they found difficult to explain.

It was a matter of preserving honor, a matter of not letting Syria create a situation where it or its allies or surrogates could credibly claim to represent the aspirations of Palestinians.

"Why did the Jews fight a useless battle in the Warsaw ghetto? For their dignity. For their honor," said a spokesman for PLO leader Yasser Arafat, who is in Tunis. "Maybe these things do not mean a great deal to politicians but they do to us."

Yesterday Syrian forces moved about 20 tanks near the Arafat loyalist stronghold in the camp here and it has caused some worry.

Along the frontlines with Israel in the Bekaa, the PLO fighters and spokesmen concede that Syria has them cornered, unable to move while rebel forces roam freely.

Yesterday's battle in eastern Lebanon in which rebels overran at least six loyalist bases and killed 15 loyalists and wounded 25 left their forces deployed in isolated islands, a spokesman said.

Today, fighting there was sporadic through the day but shelling became intense at nightfall, according to eyewitness reports.

In this northern stronghold, there was measured confidence that if the rebels advance and are aided by Syrian forces, there is a chance the loyalists can put up a good fight.

Syria never conquered this city, Lebanon's second-largest, where Moslem fundamentalists opposed to the Damascus regime appear to hold sway. The PLO is clearly counting on their help in the event of any outbreak of fighting here.

The fundamentalist Moslem militias headquartered in Tripoli have frequently clashed with pro-Syrian militias here in recent months and their strength apparently is the reason that Syrian forces have not attempted to enter the city.

About 40,000 Palestinian refugees are in Tripoli, including 2,000 PLO fighters. But the fighters are largely reserves, left here when the PLO regulars went to the Bekaa Valley.

There is no indication that, amid the air of pessimism, Palestinians are fleeing Tripoli. It would be hard to do so. Syrian forces surround the city and in the 50 miles between here and Beirut, there are a dozen military checkpoints--most of them Syrian, others Lebanese Army and Lebanese Christian militia--where travelers are rigorously scrutinized. Israeli gunboats patrol the coast.

From eastern Lebanon, the telephone lines of the last PLO holdouts rarely work to this headquarters, to which Arafat's military commander, Khalil Wazzir, also known as Abu Jihad, has retreated.

Abu Hajem, commander of PLO forces in the Bekaa Valley whose appointment by Arafat two months ago touched off the mutiny within Fatah, also arrived in Tripoli today, but said he intended to return shortly to the Bekaa. Abu Hajem, who had been with Arafat in the siege of Beirut, was opposed by many guerrillas already in the Bekaa and they rejected him as unqualified.