(Adds Bush statement)

By Tom Perry

BEIRUT, Feb 14 (Reuters) - The son of slain Lebanese leader Rafik al-Hariri on Thursday called for reconciliation with his Syria-backed opponents, extending an olive branch on the third anniversary of the killing. Supporters of Saad al-Hariri's anti-Damascus governing coalition poured into Martyrs Square to mark the assassination which led to Syria's military withdrawal from Lebanon and the deep political conflict which now paralyses the country.

"Our hand is extended and will remain extended, no matter what the difficulties," Hariri told the crowd in a message to the opposition, which is led by the powerful Damascus-backed Hezbollah.

The governing coalition accuses Syria of killing Hariri and other anti-Syrian figures assassinated since his death. Syria denies any involvement.

Speaking at the funeral of assassinated Hezbollah military commander Imad Moughniyah, Hezbollah leader Sayyed Hassan Nasrallah said: "When we see that the extended hand is sincere, it will only be met by an extended hand."

The opposition and governing coalition have been locked in a power struggle for 15 months that has paralysed government, left the country without a president since November and led to the worst street violence since the 1975-90 civil war.

Both sides have agreed on General Michel Suleiman as the nominee for president. But his election by parliament has been postponed by a dispute over the division of seats in the new cabinet.

Addressing the opposition, Hariri said: "We call on you to elect General Michel Suleiman president of the republic now and not tomorrow so that we can sit together in a government of national unity."

"THE TRUTH IS COMING"

Waving Lebanese flags, governing coalition supporters held aloft pictures of Hariri and the other anti-Syrian figures assassinated since the Feb. 14, 2005 suicide truck bombing that killed the former prime minister and 22 others.

A bronze statue of Hariri was unveiled at the site of the blast on the Beirut seafront.

"Our one and only goal is to continue the legacy of the martyr Prime Minister Rafik al-Hariri -- the legacy of coexistence and construction," said Hariri, pledging that he would also pursue justice for victims of the assassinations.

The U.N. Security Council voted last year to set up an international tribunal to try suspects in the killings.

"The truth is coming," Hariri said, addressing the crowd estimated at more than a million by Interior Minister Hassan al-Sabaa. Others put the crowd, which gathered under a stormy Beirut sky, in the tens of thousands.

U.S. President George W. Bush marked the anniversary by calling on Syria and Iran to "end their efforts to undermine Lebanon's legitimate government and to interfere in its political process".

Hariri's assassination triggered international pressure that forced Syria to end a 29-year military presence in Lebanon.

The withdrawal was followed by parliamentary elections which gave the anti-Damascus coalition its majority in the chamber and control of government. The governing alliance accuses the opposition of seeking to restore Syrian control.

Lebanon is one of the sources of conflict between Damascus and Washington -- a strong backer of the Beirut governing coalition, which is also supported by Saudi Arabia, another country with bad relations with Syria. (Editing by Ibon Villelabeitia)

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