By Laila Bassam

BEIRUT, May 25 (Reuters) - Lebanon's parliament is set to vote in army chief General Michel Suleiman as the country's 11th president on Sunday, filling a post left vacant for six months by a crisis that threatened a new civil war.

A Qatari-brokered deal between rival Lebanese leaders last week defused 18 months of political stalemate that erupted into street fighting this month and led to Iranian-backed Hezbollah fighters seizing Beirut and routing government loyalists.

Members of parliament from the U.S.-supported ruling majority and the Hezbollah-led opposition will attend a parliamentary session at 1400 GMT to elect Suleiman as president, as stipulated by the Doha agreement. The vote had been postponed 19 times because of the crisis.

The deal also calls for the formation of a national unity government where the opposition has veto power and a new law for the 2009 general election.

The agreement aims to defuse a conflict that has stoked sectarian tensions, paralysed government and the country's constitutional institutions, and battered the economy.

Parliament has not met for more than a year and a half, during which time the government of Prime Minister Fouad Siniora has barely functioned. Bouts of violence claimed scores of lives and revived memories of the 1975-90 civil war.

Sunday's vote will be attended by Qatar's emir and his prime minister -- the driving force behind the Doha agreement -- and a host of foreign ministers, including those of arch-rivals Syria and Saudi Arabia as well as of France, Turkey and Iran.

Saudi Arabia and France back the government while Iran and Syria support the opposition. No U.S. administration official is expected at the session.

SYRIAN ERA

Lebanon's complex power-sharing system stipulates that the country's president should always be a Maronite Christian, the prime minister a Sunni Muslim and the speaker of parliament a Shi'ite.

Suleiman fills a chair vacated in November by Emile Lahoud, an ally of Damascus seen by his opponents as a Syrian stooge. Appointed army chief in 1998 when Damascus controlled Lebanon, Suleiman is inescapably linked to the Syrian-dominated era.

He coordinated closely with Syrian troops before they were forced to withdraw from Lebanon in 2005 by Lebanese and international pressure triggered by the assassination of former Prime Minister Rafik al-Hariri.

As president, Suleiman will have to grapple with a slew of divisive issues including a U.N. Security Council resolution that calls for all militias in Lebanon to be disarmed -- a demand supported by Hezbollah's Lebanese opponents.

But his first task is to appoint a new prime minister and coordinate with him the formation of the new cabinet. The leader of the parliamentary majority, Saad al-Hariri, is the frontrunner for the job.

Suleiman's profile soared nationally during 15 weeks of fighting between the army and al Qaeda-inspired Islamist militants who launched an insurrection in the north a year ago.

Lebanese rallied around the troops during their campaign against the militants in a Palestinian refugee camp. More than 420 people, including 169 soldiers, were killed in the fighting before the revolt was put down.

Fluent in English and French, Suleiman is married with three children. He graduated from the Military Academy in 1970 and holds a Lebanese University degree in politics and administration. He was born in the Christian village of Amchit. (Writing by Nadim Ladki; Editing by Catherine Evans)

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