But the legal document, a step towards establishing the court, does not come into force until it is ratified by the Lebanese parliament, which has not been called into session because of the refusal of its speaker to do so.

The tribunal has become a contentious issue between the anti-Syrian government of Prime Minister Fouad Siniora, which wants the court, and pro-Syrian factions that include President Emile Lahoud, parliamentary speaker Nabih Berri and the Shiite Hezbollah movement, who oppose it.

U.N. chief legal counsel Nicolas Michel signed the agreement, which has also been approved by an official in Lebanon's justice ministry.

The United Nations is hoping that a solution will be found by Arab diplomats and others, who are attempting to defuse the crisis and break the political logjam.

A senior U.N. official said the world body was willing to explain the impartiality, scope and limitations of the tribunal to its opponents if that would resolve the impasse over the court.

Sources: Reuters