Lebanon's pro-Syrian president refused to endorse a draft accord sent to him by the Cabinet to create an international tribunal to try suspects in the assassination of a former premier. President Emile Lahoud said Saturday the Cabinet of Prime Minister Fuad Saniora and his anti-Syria allies had lost its constitutional legitimacy. The president's action was certain to intensify political and sectarian tensions that have worsened since mass protests over the 2005 slaying of former prime minister Rafik Hariri forced Syria to end a nearly three-decade military occupation of Lebanon. The Syrian-backed Hizbullah guerrilla group and its allies were in the ninth day of street protests launched after talks with Saniora's government failed to produce a national unity government. The groups called for a huge demonstration Sunday, saying it would mark an escalation in their attempt to oust the US-backed government. The political crisis has taken dangerous sectarian lines, with most Sunni Muslims supporting the Sunni prime minister and Shiites backing Hizbullah. Christian factions are split between the two camps. A Christian leader allied with Hizbullah, Gen. Michel Aoun, renewed his call for Saniora to step down as a way out of the political impasse. "Your excellency, the prime minister, stop being stubborn ... Go home," Aoun said in a televised statement Saturday. "That's better for you because you are unable to steer the ship no matter how much support you get from abroad. Please step down." The president had been expected to reject the tribunal agreement sent to him Nov. 27. The accord calls for a UN-organized court to try the suspected assassins of Hariri, an opponent of Syrian influence who was killed by a truck bomb along with 22 others in February 2005. A UN investigation has said the attack's complexity suggested the Syrian and Lebanese intelligence services played a role in the assassination. Syria denies involvement. In a statement issued by his office, Lahoud said he was returning the tribunal accord to the Cabinet "for reviewing as soon as a constitutional and legitimate Cabinet is formed." He and others in the opposition argue Saniora's government is unconstitutional because six pro-Syria Cabinet ministers, including all the Shiite Muslims, resigned last month shortly before the government approved the tribunal. The move caused Lahoud, a Christian, to say the government should step down because the constitution requires all of Lebanon's sects to be represented in the Cabinet under the sectarian power-sharing political system. Saniora has refused to resign, saying Cabinet meetings still have the quorum necessary to make decisions. The Hariri tribunal has become the latest weapon in the battle between pro- and anti-Syria factions over the demand by Hezbollah for a third of the Cabinet's seats, which would give the group and its allies veto power over key decisions, including the accord for the UN tribunal. The accord not only requires the Cabinet's approval but also the endorsement of Lahoud and the Parliament, where anti-Syria forces hold a majority. But the UN Security Council could bypass Lebanon and set up the tribunal on its own. The tribunal is envisioned to include a majority of foreign judges and a minority of Lebanese judges. Saniora's Cabinet is expected to refer the accord to Parliament for approval even without Lahoud's signature. But the Parliament speaker, Nabih Berri, a Hizbullah ally, has signaled he will not convene the assembly to endorse the document.