Rival Shiite Moslem militias began pulling their fighters out of Beirut on Saturday as the Syrian-backed government took its first step toward consolidating control over Lebanon's capital.

Militiamen of the pro-Syrian Amal, or Hope, and the Iranian-backed Hezbollah, or Party of God, were each pulling forces from the Beirut area. Across the city in Christian east Beirut, militia of the Lebanese Forces, under Samir Geagea, were gathering to prepare for departure before the government's Nov. 19 deadline.A government source said a force of 9,000 soldiers under Gen. Emile Lahoud, the government's commander, would begin taking over greater Beirut on Friday. The source spoke on condition of anonymity.

The unification of Beirut, divided into Moslem and Christian sectors since the outbreak of the civil war in 1975, is a key element in a peace plan sponsored by the Arab League. The war has left at least 150,000 people dead and shattered a once booming economy.

Syrian officers and Iran's ambassador to Damascus, Hassan Akhtari, were in west Beirut on Saturday to supervise the implementation of a peace accord between Amal and Hezbollah. A three-year power struggle between them has left more than 1,100 people dead.

Syria, with 40,000 troops deployed in Lebanon, is the most powerful enforcer of the Arab peace plan.

The Amal-Hezbollah accord was reached last week in Syria's capital, Damascus. Amal and Hezbollah sources said the militias would exchange prisoners Monday in south Lebanon's Iqlim al-Tuffah, or Apple Province.

The government source said the army has a 500-member battalion ready in south Lebanon to move into the province after the withdrawal of Amal and Hezbollah fighters. But he said the deployment there was not expected immediately.

"The army wants first to consolidate its control over Beirut," he said.

Greater Beirut stretches along a 15-mile coastal strip from the Dog River in the north to the Damour River in the south.