The UN has taken a further step towards creating an international tribunal to try suspects in the killing of the former Lebanese premier Rafik Hariri.
Political splits have an unsettling effect on war-weary Lebanese
It signed an accord sent by Lebanon's Western-backed government to set up the panel, but the move must also be ratified by parliament, the UN said.
Analysts say that will be a difficult process in the deeply divided body.
Lebanon's pro-Syrian president, Emile Lahoud, and pro-Syrian parties in parliament vigorously oppose the plan.
The accord was signed by the UN's top legal affairs official, Nicolas Michel, in New York on Tuesday and was returned to Lebanon for ratification.
"It is up to the competent Lebanese authorities to take the steps necessary under the Lebanese constitution for the approval and ratification of the agreement, to allow it to enter into force," a UN statement said.
Mr Lahound accused the government of Prime Minister Fuad Siniora of violating the constitution by signing the accord and sending it to the UN last week.
The pro-Syrian speaker of parliament, Nabih Berri, has so far refused to convene parliament to discuss the issue.
The UN Security Council approved creation of the panel last November to try suspects in the killing of Mr Hariri and 22 others in Beirut two years ago.
But the move sparked a crisis within Lebanon's national unity coalition, with pro-Syrian ministers quitting over plans to approve the tribunal.
The cabinet, which does not now contain representatives from all the different sects in Lebanon, is considered illegitimate and unconstitutional by opponents.
Damascus is widely suspected of having a hand in the Hariri bombing, a charge denied by the Syrian government.
Interim UN reports have implicated top Syrian officials in Hariri's death, suggesting it was highly unlikely that the complex plot to kill him could have been hatched and carried out without Syria's knowledge.