Israel's invasion of Lebanon and the continuing dismantlement of the Palestine Liberation Organization have left Palestinian nationalists in the occupied West Bank deeply dispirited and with a sense of having been betrayed by the Arab world.

The only elected large-city mayor remaining in the West Bank, Elias Freij of Bethlehem, said today that he is planning to resign, along with Gaza Mayor Rashid Shawa, and that he expects all the Arab leadership in the occupied territories to be replaced imminently by Israeli-appointed "quislings."

Palestinians of varying degrees of nationalistic intensity said in interviews that they regard the West Bank and Gaza "lost" to Israel, and that an expulsion of PLO guerrillas from Lebanon will be closely followed by a complete suppression of nationalist expression in the territories Israel captured 15 years to the day before the start of the invasion of Lebanon.

"You can imagine, for the first time we realize we are totally isolated, totally cut off from our leadership in Lebanon and from the Arab world. We are paralyzed. We can't say anything, and anyway, who would care what we say now?" asked Freij, a moderate who long has advocated mutual PLO-Israel recognition as the only course to avert Israeli annexation of the West Bank.

Freij said he expects to submit his resignation in about two weeks, or as soon as the outcome of the Israeli Army's siege of Beirut is clear, adding that "it would be unwise of me to quit now, when our leadership is fighting for their lives in the Beirut enclave." He said that he and Shawa, a close political ally, had decided not to give the Israeli occupation government the "satisfaction" of firing them.

The mayors of all the other principal towns in the West Bank already have been deported or summarily dismissed, and the Israeli authorities yesterday dismissed the elected municipal councils of Nablus and Dura, near Hebron, as part of a newly announced plan to appoint moderate Arabs following the defeat of the PLO in Lebanon.

Beginning in March, the occupation government began firing the mayors of Nablus, Ramallah, Al Birah and several other towns, and replacing them with Israeli officers until moderate Arab leaders could be found. The dismissals triggered the worst rioting in Israel's occupation of the West Bank and Gaza, leaving 15 Palestinian youths shot dead by Israeli soldiers and Jewish settlers and about 200 wounded.

"I feel betrayed. All the Palestinians feel betrayed. The PLO was deceived by the Arab states, who didn't lift a finger to help the PLO in Lebanon. The PLO didn't realize the full strength of the Israeli military machine, as we do inside," said Freij.

Citing an Arab proverb--"You can't shave one side of your face and not the other"--Freij said he expects Israel to impose a political solution for the West Bank after it creates a "new political order" in Lebanon.

"They will find collaborators. When there is thunder and it rains, the snakes come out from under the rocks. Now, there is the thunder of cannon and the rain of Palestinian and Lebanese blood, and the snakes will come out again," the mayor said. He said he expects West Bank administrator Menachem Milson to replace PLO supporters who were elected in 1976 with followers of the Village Leagues, an Israeli-financed political organization that was expanded by Milson as an alternative to the nationalist mayors.

Appearing to be more dispirited than he has in numerous conversations during the past four years, Freij tried to put the best possible face on the future of West Bank Palestinians.

"The odds now are against us, but believe me, the Palestinian nation will not die. Maybe some Arab states will die, but not the Palestinians," he said. Then, shrugging his shoulders in seeming contradiction, Freij added, "But I'm afraid the Arabs will lose the West Bank. The Israelis are determined to have a Jewish West Bank, and time is on their side. Who knows, by the end of the year we may not exist."

Mohammed Shadid, a professor at Najah University in Nablus, said he expects whatever PLO leadership that survives the Lebanon invasion will become more extreme as it moves its base of organization elsewhere, possibly Algeria or South Yemen. At the same time, West Bank youths, who have limited their protests largely to rock-throwing demonstrations, also will become more extreme, forming new urban guerrilla units and concentrating their attacks on Israel's civilian population, Shadid said.

"They the Israelis may think they have peace in the Galilee, but they will have hell in Tel Aviv and Jerusalem. You can't pacify every 14-year-old Palestinian. Maybe you can subdue them for a while, but not permanently," he added.

Shadid noted that already since the June 5 invasion there have been numerous strikes and violent protests in the West Bank, including one in which a youth was shot to death by Israeli troops in Nablus. Bethlehem University was closed following protests against the invasion.

"There seems to be an increased willingness to sacrifice and say, 'Okay, we have to go it alone.' I think there will be more Black June groups being formed," Shadid said, referring to a radical PLO splinter that is believed to have been behind last month's attempted assassination of Israel's ambassador to London. That shooting sparked the Israeli retaliation raids that preceded the invasion.

Ramonda Tawil, a Palestinian author and well-known nationalist activist, said that the West Bank is still in a "state of shock," but that she expects an escalating cycle of violence prompted partly by Israeli anti-Arab hatred stemming from the deaths of 214 Israeli soldiers in Lebanon and rising West Bank passions over the uncounted deaths of Palestinians in Lebanon.

"Now the names of the Palestinian martyrs are starting to come back to the families left in the West Bank. You can imagine what will happen. From the Israelis, we expect all the anger over the war to go against us, and there will be even more killing," said Tawil.

Freij has been saying publicly for months that if the PLO failed to moderate its stand and establish a dialogue with Israel, the West Bank would become de facto part of Israel. Today he said events had proved him correct.

"I was begging, shouting and crying that we had to make some sort of move, that a military solution to our problem was out of the question. Nobody seemed to listen, but now I am getting telephone calls from people saying 'Why didn't we listen to Freij?' " the mayor said.

He added, "Now I feel lonely. Who is left to speak out? What is there left to say?"