* March 8 boycott deprives parliament of quorum
* Search for president may take months
* Syrian war deepens longstanding political rifts (Adds U.S. comment)
BEIRUT, April 30 (Reuters) - Lebanese politicians abandoned their second attempt to elect a new president on Wednesday after dozens of deputies boycotted a parliamentary vote to choose a successor to President Michel Suleiman.
The country's two main political blocs, the pro-Hezbollah March 8 alliance and its March 14 rivals, have yet to agree on a consensus candidate who could garner majority support among the 128 parliamentary deputies.
The stalemate stems from longstanding political and sectarian divisions deepened by the three-year-old war in neighbouring Syria, and could drag on well beyond the end of Suleiman's term on May 25.
Shi'ite Muslims support President Bashar al-Assad while Sunni Muslims back the rebels fighting to topple him. Maronite Christians, who are allocated Lebanon's presidency under the country's confessional power sharing system, are split.
Last week former warlord Samir Geagea, a longtime opponent of Assad, won 48 votes with the backing of March 14 deputies. His total was eclipsed by the 52 blank voting slips returned by the pro-Assad March 8 politicians.
Former army chief Michel Aoun, who is part of the March 8 alliance, has said he will stand if a consensus emerges to support him.
In the absence of any such agreement, Wednesday's vote was called off after Aoun's March 8 allies stayed away from parliament, depriving it of a two-thirds quorum necessary for the vote to go ahead.
The parliament's speaker scheduled the next attempt at a vote for May 7, less than three weeks before Suleiman's term expires.
Senior Lebanese politicians have said that talks to find his successor may drag on for several months and high profile candidates are unlikely to win broad support in the polarised political climate, meaning the choice may settle ultimately on a relatively obscure and less divisive figure.
The search for a new president comes one month after Prime Minister Tammam Salam, appointed in March last year, finally ended a year-long government vacuum when he won a vote of confidence in his new cabinet.
A prolonged delay in electing a president could put Lebanon back in limbo just when it most needs leadership to contain months of sectarian conflict and cope with a flood of Syrian refugees and a sharp slowdown in economic growth.
U.S. State Department spokeswoman Marie Harf said Washington hoped the election of a new Lebanese president would progress "in accordance with the Lebanese constitution on time and free from foreign interference". (Reporting by Dominic Evans in Beirut; Additional reporting by Will Dunham in Washington; Editing by Jeremy Gaunt)