Beirut — Lebanese opposition forces have begun to consolidate, with growing indications that the beleaguered country may be in for a new round of internal strife.
Two prominent Muslim leaders have predicted a new civil war if the Christian-dominated government does not soon introduce changes to end the uneven distribution of power among rival sects, one of the main causes of the civil war in 1975-76.
The statement, made in Damascus, was significant because it showed that rival Muslim groups are merging forces to resist decisions by the government of President Amin Gemayel.
And it does have weight behind it, for Walid Jumblatt, leader of the Druze and Lebanon's leading leftist, and Nabih Berri, head of the Shiite ''Amal'' organization, both control sizable militias.
Mr. Jumblatt controls the most militant fighters, while Mr. Berri leads Lebanon's largest sect. Throughout the eight years of violence, the two key figures have never before joined forces.
The union was related to the expected deployment of the Lebanese Army in the Shouf mountains after a partial Israeli withdrawal. The Shouf has been the site of intermittent battles between Christian and Druze militias, and the Muslims fear the Christian-dominated Army will attempt to overwhelm, even massacre, the Muslims.
''The two sides strongly reject the entry of the Lebanese Army into the mountain areas and are ready to confront it whatever the consequences may be,'' the statement said.
The pledge appeared to have been put to the test over the weekend, when the Israeli Army handed over control of two villages, Ain Saad and Monteverde, to the Lebanese Army. The surprise move was seen by the Beirut press as a ''dress rehearsal'' for an imminent Israeli pullback from the Shouf.
Almost immediately, fighting broke out between Christian and Druze gunmen in nearby areas. And on Monday, Mr. Jumblatt was quoted in Jordan as saying, ''If President Gemayel does not accept political solutions and is determined to fight the Druze side, then we are willing to fight the Lebanese Army endlessly.''
More subtle signs of growing opposition have also surfaced among moderate Muslims. During a rally held to observe the Islamic holy month of Ramadan last week, Lebanon's grand mufti, Sheikh Hassan Khaled, declared, ''Lebanon's fate cannot be determined by a single group, party, or sect, but by a national decision.''
And at a major celebration to end Ramadan, he added that the government must treat Christians and Muslims equally. ''Do not weigh Lebanon with two sets of scales,'' he said, adding that a national congress should be held to finally win agreement on terms for reconciliation.
Suspicions among Muslims about long-term Christian intentions were underlined last week by former Prime Minister Selim al-Hoss, a Sunni Muslim moderate. He criticized Pierre Gemayel, founder of the Christian Phalange Party and father of the President, for hypocrisy.
Mr. Gemayel recently called on all factions to support the government. But he made the speech at the opening of a new military complex opened by the Phalange militia, technically now an illegal force.
''We (Muslims) cannot reconcile such a display,'' Mr. Hoss said afterward. It has been noted by several Muslims that their own militiamen were disarmed, and many detained, while the Christian forces still operate their own mini-state.
Reaction to the Jumblatt-Berri statement, however, showed the level of dissent among Muslims, indicating that words alone could once again bring out the deep divisions that still exist among competing religious and political forces in Lebanon.
Mohsen Ibrahim, head of the Communist Action Oganization, said the declaration ''enjoys the support of all Lebanese nationalists. It has come as (an) expression of commitment to the option of national resistance . . . to factional fascist hegemony,'' a reference to rightist Christian control.
The predominantly Shiite communist group is one of the main forces still active, particularly behind Israeli lines.
However, Pierre Gemayel warned about the same time of ''an all-out revolution where there will be a vanquished and a victor if the will of the legitimate authorities is not imposed.''
President Gemayel has made some limited attempts to reconcile the rival groups. For the first time in many years, a Christian chief of state offered an iftar banquet in honor of the Islamic Ramadan, to which all key Muslim and Christian clergy and politicians were invited.
Although many attended, some, like Mr. Berri, did not. He said later that ''problems are not solved at banquets.''