Lebanon has been without a head of state for more than seven months, and the last bid to elect a president was held on January 19.

The vote for the presidency, reserved for a Maronite Christian under Lebanon's delicate sectarian power-sharing system, pits the Hezbollah-backed Sleiman Frangieh against financial official Jihad Azour, who has mainly been endorsed by Christian and independent legislators.

With no side appearing to have the numbers to get their candidate across the line, analysts say the vote could further entrench a political stalemate, dimming hopes of saving the economy after three years of meltdown.

"It's very unlikely that this session will end with the election of a president," analyst Karim Bitar said.

As the 11 before it, Wednesday's attempt would likely "only be a way for political forces to gauge their respective electoral weight" and see how many votes they can get, he added.

Lebanon is facing a double power vacuum, with the country governed by a caretaker cabinet with limited powers for more than a year.

By convention, the premiership is reserved for a Sunni Muslim and the post of parliament speaker goes to a Shiite Muslim.

The international community has urged politicians to elect a consensus presidential candidate who can help the country enact reforms required to unlock billions of dollars in loans from abroad.

Frangieh, a former lawmaker and minister who is a friend of Syrian President Bashar al-Assad, hails from a storied family dynasty, like many of Lebanon's prominent political figures.

On Sunday, he promised to be "the president of all Lebanese" despite his polarising alliances.

Azour was finance minister from 2005 to 2008 and has stepped aside from his role as the director of the Middle East and Central Asia department at the International Monetary Fund in view of the presidential contest.

'Prolonged vacuum'

The winner needs two-thirds majority, or 86 votes from the 128 members of parliament -- but Hezbollah and its allies have posted spoilt ballots to disrupt previous votes.

Quorum has been lost before a second round of voting -- where the winner only requires 65 ballots -- has been able to go ahead.

Hezbollah and its allies adopted a similar tactic in the last presidential vote, a move that left Lebanon without a president for more than two years, until Michel Aoun's 2016 win.

If Azour gets more than 60 votes it would be a huge "reversal of fortune for Hezbollah", said Bitar, and would represent massive cross-sectarian "opposition to Hezbollah hegemony on the Lebanese political landscape".

"However, at this stage, the most likely scenario is a prolonged vacuum," Bitar added.

Azour on Monday said he wanted to "contribute to a solution" not a crisis, as he announced his bid for the post.

He said he was "not defying anyone", after Hezbollah described him as the "defiance and confrontation candidate".

Mohammed Raad, the head of Hezbollah's parliamentary bloc, has accused Azour's supporters of not wanting him to be elected but "using him" to block Frangieh's path to the presidency.

Bitar said a stalemate at Wednesday's ballot could pave the way for protracted negotiations "that would ultimately reach a third-man solution".

The United States and France on Tuesday renewed calls for Lebanese lawmakers to cooperate and elect a new president.

French foreign ministry spokeswoman Anne-Claire Legendre urged MPs to "take this date seriously" and "not to waste another opportunity".