By Crispian Balmer BEIRUT, Dec 10 (Reuters) - Hundreds of thousands of opposition protesters, led by the pro-Syrian group Hezbollah, are expected to stage a rally on Sunday aimed at ousting Lebanon's Western-backed government. Opposition supporters have been camping out in central Beirut since Dec. 1, paralysing the heart of the capital and vowing not to budge until Prime Minister Fouad Siniora bows to their demands for a government of national unity. Siniora and the Sunni-led ruling majority refuse to give in, accusing the Shi'ite Hezbollah of trying to stage a coup in the wake of their 34-day war against Israel earlier this year. Hezbollah chief Sayyed Hassan Nasrallah claimed a "divine victory" in that conflict and said on Thursday that Siniora had tried to prevent supplies reaching his guerrilla forces during the fighting -- a charge the prime minister swiftly denied. Commentators have warned that the worsening stand-off could degenerate into wide-scale violence in a country that is still trying to rebuild after the 1975-90 civil war. However, political sources in the anti-Syrian government say no political solution or compromise is in sight. A U.S. State Department official on Saturday accused Syria and Iran, Hezbollah's allies, of trying to destabilise Lebanon and said the situation was of "very significant concern". Speaking in Kuwait, Deputy Assistant Secretary James Jeffrey said Washington was trying to mobilise moderates in the Middle East to support the Lebanese administration. TWO CAMPS The struggle is between two broad alliances, with the ruling coalition made up of Sunni Muslim, Druze and some Christian parties confronting Hezbollah, another Shi'ite group and a Christian party headed by former General Michel Aoun. "Mr prime minister go home, it's better for you because you cannot captain the ship," Aoun said on Saturday, repeating opposition accusations that Siniora was a U.S. vassal. When the opposition launched their protest 10 days ago, as many as 800,000 people took to the streets -- almost a sixth of the population of Lebanon, which lies at the eastern end of the Mediterranean between Israel and Syria. In the following days there have been regular rallies in the tent city that has sprung up in two central squares but no further mass mobilisation of opposition forces. Sunday's protest is due to start at 3 p.m. (1300 GMT) The last time Lebanese took to the streets to demand a change of government was in 2005, when the so-called "cedar revolution" successfully forced out the Syrian army, which had held dominion over the country since the calamitous civil war. Lebanon's main Shi'ite groups originally joined the new government, but they quit last month and Nasrallah says their departure rendered the cabinet unconstitutional. The Hezbollah leader has warned that, if Siniora does not agree to give the opposition power of veto in a new government, he will push for elections three years ahead of schedule. Siniora's allies say Hezbollah simply wants to derail plans to set up an international tribunal to try suspects in the 2005 assassination of former Prime Minister Rafik al-Hariri, which many Lebanese blame on Syria, a charge Damascus denies. Lebanon's pro-Syrian President Emile Lahoud refused on Saturday to endorse plans for the court, saying the depleted cabinet had acted unconstitutionally last month when it had moved to approve the project.
