* Politician close to Hezbollah and allies concedes defeat
* Anti-Syrian bloc's win welcome news for U.S., Saudi allies
(Adds details, background)
BEIRUT, June 7 (Reuters) - An anti-Syrian coalition defeated Hezbollah in Lebanon's parliamentary election on Sunday in a blow to Syria and Iran and a boost to the United States.
"Congratulations to Lebanon, congratulations to democracy, congratulations to freedom," the coalition's leader Saad al-Hariri said in a victory speech at his mansion in Beirut.
The outcome was also welcome news for Saudi Arabia and Egypt, which back Hariri's "March 14" alliance - the date of a 2005 rally against Syria's military presence in Lebanon.
"We have lost the election," conceded a senior politician close to the bloc of Shi'ite groups Hezbollah and Amal and Christian ally Michel Aoun.
"We accept the result as the will of the people."
The vote will be viewed as a stinging setback to Aoun, who held the biggest bloc of Christian MPs in the outgoing assembly and had hoped to seal his claim to speak for the Christians.
A source in Hariri's campaign predicted a decisive victory, with his bloc taking at least 70 of the assembly's 128 seats.
Perhaps 100 of the seats were virtually decided in advance, thanks to sectarian voting patterns and political deals, with Sunni and Shi'ite communities voting solidly on opposing sides.
The real electoral battle centred on Christian areas, where Aoun was up against former President Amin Gemayel's Phalange Party, Samir Geagea's Lebanese Forces and independents.
Lebanon's rival camps are at odds over Hezbollah's guerrilla force, which outguns the Lebanese army, and ties with Syria, which dominated Lebanon for three decades until 2005.
The likeliest outcome of the poll is another "national unity" government, analysts say.
SINIORA WINS SEAT
According to unofficial results, Prime Minister Fouad Siniora, who has enjoyed Western and Arab support, won a parliamentary seat in the mainly Sunni southern city of Sidon.
Siniora, 66, has headed the cabinet since the Hariri-led coalition won the 2005 parliamentary election. He led the government through 18 months of political conflict with Hezbollah and its allies, but is not expected to keep his post.
Voting was relatively trouble-free across Lebanon, although there were many reports of vote-buying before the poll, with some Lebanese expatriates being offered free air tickets home.
The United States, which lists Hezbollah as a terrorist group, has linked future aid to Lebanon to the shape and policies of the next government. Hezbollah, which says it must keep its arms to deter Israel, is part of the outgoing cabinet.
The anti-Syrian coalition has enjoyed firm backing from many Western countries since the 2005 assassination of Hariri's father Rafik al-Hariri.
The coalition took power in an election following Hariri's killing, but struggled to govern in the face of a sometimes violent conflict with Hezbollah and its allies.
Hezbollah MP Hassan Fadlallah said any new government had to be based on partnership, not on one side monopolising power.
"Whatever the results of the election, we cannot change the standing delicate balances or repeat the experiences of the past which led to catastrophes on Lebanon," he told Reuters.
"Whoever wants political stability, the preservation of national unity and the resurrection of Lebanon will find no choice but to accept the principle of consensus."
Hezbollah and its allies insisted on being given veto power in a unity cabinet -- a demand that caused an 18-month political deadlock until it was granted under a Qatari-brokered deal that followed street fighting in Beirut in May 2008.
Leading anti-Syrian politician Walid Jumblatt said he opposed the idea of veto power for the opposition.
Asked if they should be in the government, he told Reuters: "Yes, but I cannot decide on my own. I am part of a coalition and it should be a unanimous decision."
Tensions in Lebanon have mostly been kept in check since the Qatari-mediated accord dragged the country back from the brink of civil war. A thaw in relations between Saudi Arabia and Syria has also helped maintain stability in recent months.
Security was tight, with 50,000 troops and police deployed across Lebanon, especially in the most contested districts.
Security sources said one person was wounded by gunfire in the northern city of Tripoli and there were brawls between rival supporters elsewhere, but no reports of serious fighting.
Baroud said preliminary figures showed a turnout of more than 54 percent, a high figure for Lebanon, where hundreds of thousands of the 3.26 million eligible voters live abroad. (Writing by Alistair Lyon; Additional reporting by Nadim Ladki, Tom Perry and Yara Bayoumy; editing by Janet McBride)
Our Standards: The Thomson Reuters Trust Principles.