Beirut — The mutiny within Fatah, the backbone of the Palestine Liberation Organization, appears to be gaining strength despite efforts by chairman Yasser Arafat to end the most serious threat to his 15-year leadership.
Mr. Arafat has made almost daily trips to Palestinian bases in northern and eastern Lebanon since the power struggle broke out almost four weeks ago. But the rebellion has not been quelled, and the mutineers have gained new backers.
A move to cut off supplies, food, pay, and fuel has been unsuccessful, since the rebels responded by seizing six supply depots in Damascus over the weekend and attempted to take control of a major training base.
The threat has become so serious that loyal Fatah guards have now been positioned around all key PLO offices and installations.
And the Voice of Lebanon, a private Christian radio station, reported that there had been an assassination attempt on Arafat during his visit to Lebanon on Monday, in which a bodyguard was killed.
PLO officials described the claim as ''total fabrication and baseless.'' But increased security and secrecy about Arafat's movements reflect the deepening concern about threats to his life as well as his leadership.
The Beirut press has also reported that the guerrilla leader was considering moving his main military operations center from Damascus to the northern Lebanese port city of Tripoli to decrease reliance on the Syrians. Abu Jihad, PLO deputy commander, has also denied these claims.
However, the fact that the reports were even deemed possible underlines the depth of the rebellion against the entire military and political strategy of Arafat and the PLO moderates.
It increasingly appears Arafat may have to alter his strategy in order to quell the revolt, a move that would have serious repercussions to United States peace efforts in the Middle East.
The rebels, led by Abu Musa, deputy commander of the PLO operations room, are demanding several radical moves: an explicit PLO commitment not to withdraw forces from Lebanon; the return of all fighters from the other seven Arab states where they were dispersed after evacuation from Beirut; an end to the dialogue with Jordan on peace terms with Israel; change in military commanders; and a special committee to investigate corruption within the PLO.
Since the debacle in Beirut during the Israeli invasion and the subsequent scattering of the PLO fighters throughout the Arab world, Arafat has found it increasingly difficult to resist pressure from the radicals. And the recent backing of the rebels by the Marxist ''Democratic Front'' (DFLP) faction on the issue of change of two military commanders could make compromise even more difficult. It also suggests that the dissension over Arafat's strategy may spread throughout the multifaceted organization.
There have been suggestions in Damascus that the moderates may attempt to hold a ''revolutionary court'' to try the rebels. But there are also fears that this could lead to a repeat of the court-martial and subsequent breakaway of Abu Nidal, the renegade whose faction has been responsible for assassination attempts on Palestinian leaders and the Israeli ambassador to London that triggered the invasion of Lebanon.
The split within Fatah, the largest of the eight factions which make up the PLO, has in turn led to small-scale splits within the Arab world.
Hard-line Libya has openly supported the revolt. Khaled Hassan, one of the five founders of Fatah, charged that a north African state, presumably Libya, has provided $34 million for the campaign to topple Mr. Arafat in favor of a more militant leadership.
And Syria has tacitly aided them by allowing free movement and free speech at press conferences.
In turn, however, Saudi Arabia appears to be trying to aid Arafat. After a Cabinet session Monday, when the rebellion was discussed, one Saudi official said King Fahd was ''extremely concerned.'' And he hinted that the kingdom was taking steps to end the rift, in part by urging Syria to limit its support.
Arab involvement is in part generated by concern that the dispute will further weaken the Arab world's position at a time unity is needed in terms of negotiations with Israel.
Arafat may even be attempting to draw the Soviet Union into the problem to help mediate with Arab hard-liners. In Tripoli Monday, he received a Soviet diplomatic delegation and the rift within Fatah was reportedly discussed.