BEIRUT - Lebanon's opposition will boycott a parliament session to elect a new president on Friday with no deal among leaders on who will replace the pro-Syria incumbent, whose term ends the same day, a senior opposition source said.

The anti-Syrian governing coalition said on Thursday it would go to the session to elect a replacement for President Emile Lahoud. But the boycott by the Damascus-backed opposition means there will be no two-thirds quorum for the vote.

Many fear Lahoud's departure from office with no deal on his successor could result in two rival administrations and violence in a country still rebuilding from its 1975-1990 civil war.

French-led efforts have failed to forge agreement between the governing coalition and the opposition, which includes the powerful Hezbollah. The election has already been postponed four times.

Lahoud has said he will take action before leaving office if there is no deal. Like the opposition, he says the government of Prime Minister Fouad Siniora is illegitimate.

Although he has not said what he plans to do, one option is asking the army to take over.

"I stand by my position that this government is illegitimate and unconstitutional. If it thinks it can go on without the election because of outside backing, it will bring catastrophes on the country sooner or later," Lahoud told a Hezbollah-led delegation. "Therefore, even if I stand alone, there are duties I must perform."

AOUN PROPOSAL REJECTED

The governing coalition rejected as unconstitutional a proposal by Christian opposition leader Michel Aoun for him to name a candidate for the presidency, which is reserved for a Maronite Christian in Lebanon's sectarian power-sharing system.

Aoun said the candidate, whom he did not name, would not belong to his parliamentary bloc and would be replaced after legislative elections in the spring of 2009.

Leader of the largest Christian bloc in parliament, Aoun has insisted the presidency is rightfully his.

Lahoud and the opposition say Siniora's government lost its legitimacy when all its Shi'ite ministers resigned last year.

The anti-Syrian majority argues that Siniora's government would automatically take over presidential powers until a new head of state can be elected, a view supported by European ministers visiting Beirut on a mediation drive.

Some governing coalition members favor using their majority to pick a president in the absence of a deal.

The United States and its local allies blame Syria for the deadlock. Hezbollah and its Christian allies say the U.S.-backed majority wants to keep them from their rightful share in power and accuse Washington of trying to control Lebanon.

Troops and police tightened security in Beirut ahead of the scheduled parliamentary session. There was no military parade or other key events to mark the 64th anniversary of independence.

The ruling coalition holds only a slim majority and the opposition says the vote requires two thirds of the MPs. -Reuters