Beirut — The Palestine Liberation Organization appears to be going through one of the most troubled periods in its 19-year history as the result of internal political and military disputes.
Ranking members have admitted there was a rebellion among fighters stationed in Lebanon's eastern Bekaa Valley. It flared between supporters and opponents of chairman Yasser Arafat.
Although there have been many disputes within the PLO in the past, this one is unusual because it happened within Mr. Arafat's own Fatah faction, the largest and traditionally most stable of the PLO's eight branches.
In addition, two pamphlets have been circulating among all PLO forces, condemning moderate efforts to find a diplomatic solution to the Palestinian problem. They reflect ideological divisions at a crucial time.
And strategically, the guerrilla movement now has fewer options than at any other point since its formation in 1964 as avenues of action are being sealed off one by one.
The revolt within Fatah is the clearest indication of new tension. Palestinian sources claim the spark was the appointment to key Bekaa posts of two commanders who are in disgrace because they fled during the opening stages of the Israeli invasion last summer.
Arafat was reportedly so concerned about having men loyal to him in top positions that he overrode the original dissention. Fighters took things into their own hands, reflecting the deep divisions within a faction that accounts for 80 percent of the PLO membership.
The status of Fatah is important because Arafat has often used its numerical strength and unity to haul the smaller militant wings into line.
The friction was serious enough to warrant two trips by the PLO chief into the Bekaa, his first visits to Lebanon since the evacuation of Palestinian guerrillas from Beirut last fall.
Two pamphlets circulated to the PLO rank and file throughout the region are even more threatening to Arafat's leadership. One accused him of ''plotting to sell out the Palestinian cause to the US, Israel, and Arab reactionary regimes.''
The pamphlets call for a halt to all diplomatic attempts to reach a settlement, for a formal end to the PLO dialogue with Jordan on President Reagan's peace plan, and for a commitment to armed struggle as the only solution.
The events led to an emergency six-hour summit of the Fatah central committee in Damascus, Syria, after which PLO military commander Abu Jihad said a split had been averted.
But there were reports that officials had sent out a warning to dissidents to turn themselves in before ''deterrent measures'' were launched. This triggered speculation among diplomats about the possibility of a major purge within the PLO.
Arafat cannot afford to have his attention diverted at a time when he is struggling to keep the movement's head above water.
The Lebanese and Egyptian borders with Israel are now officially off-limits. And the collapse of talks with King Hussein has at least temporarily closed off the diplomatic option.
Only militant Syria offers shelter, forcing Arafat to go along with the rejectionist policies of President Hafez Assad - even though Arafat's top aides contend he would prefer to pursue the possibility of US-directed peace talks.
The weakness of the PLO was underlined by a recent appeal from Arafat to the Soviet Union to bring up the case of Palestinian persecution in Lebanon to the UN Security Council.
There have been a series of attacks against the Palestinian civilians formerly protected by the PLO. Threats have been made against others, including residents of Sabra and Shatila, the camps in Beirut where some 800 Palestinian and Lebanese men, women, and children were massacred last year. Arafat no longer has the clout to pressure Arab governments to work to ensure that civilians are not harassed.