BEIRUT, OCT. 29 -- Militias of the pro-Iranian Hezbollah and two Syrian-backed factions agreed today to withdraw from Beirut, heralding key progress in securing Moslem-Christian peace in Lebanon.

Security sources said most of 12 Western hostages believed to be held by the Shiite Moslem Hezbollah have already been moved out of the city's southern suburbs where the militia is based.

Hezbollah announced its willingness to withdraw after talks with a ministerial committee contacting Lebanon's warlords on a date and means for disbanding their militias in Beirut.

Earlier, Nabih Berri, chief of the 5,000-member Shiite Amal militia, and George Hawi, head of the Lebanese Communist Party's 1,000-member militia, ordered their forces to prepare to leave Beirut.

Hezbollah official Sobhi Tofeili said his men would lay down their weapons and withdraw from their stronghold in Beirut's southern suburbs. "We welcome the {peace} plan. We have no objections to it. We wish it success," Tofeili said.

The move was in response to a plan to unite Beirut -- which has been divided along sectarian lines since 1975 -- under one army, disband Lebanon's nine militias and extend legal authority across the country.

Security sources said the Western hostages believed held by Hezbollah were moved out of Beirut's southern suburbs a few days before Syrian and Lebanese troops staged an assault in Christian East Beirut on Oct. 13 to topple rebel Gen. Michel Aoun.

Hezbollah, which has dedicated itself to fighting Israel, has pledged to keep up its resistance against the Jewish state.

Berri said he had asked his Shiite followers to gather their weapons and prepare to pull out of Beirut, which would soon become free of militias and under the control of Lebanese and Syrian troops only.

Residents in the suburbs saw Amal and Hezbollah men evacuating positions and grouping heavy tanks and vehicles.

Berri did not say where he would take his weapons and forces, but political sources said they would be moved to southern Lebanon, Amal's main stronghold.

Walid Jumblatt, chief of the 10,000-member Druze Progressive Socialist Party, said he would hand over his weapons only to the Syrian army and not to the Lebanese troops, which he said he could not trust.