Hezbollah and its allies will try to overturn the majority of U.S.-backed rivals in Lebanon's parliamentary election on Sunday, which will decide the shape of government for the next four years, Reuters reported.
The election is seen as a tight contest between coalitions at odds over issues including the fate of Hezbollah's powerful guerrilla army and relations with neighbouring Syria, which dominated Lebanon until 2005.
Some polls forecast a narrow victory for Shi'ite Hezbollah, which is backed by Syria and Iran, and its allies, including Christian leader Michel Aoun.
But many expect the formation of a broad coalition cabinet, including parties from both sides, regardless of the result.
The United States, which lists Hezbollah as a terrorist group, has linked future aid to Lebanon to the shape and policies of the government that replaces the current national unity cabinet. Hezbollah is part of the present government.
The "March 14" majority coalition led by Sunni politician Saad al-Hariri has enjoyed firm backing from the United States and other countries including Saudi Arabia. It opposes the influence of Syria which dominated Lebanon until 2005.
The alliance won elections that followed the assassination of Hariri's father, Rafik, in 2005, but struggled to govern in the face of a paralysing and sometimes violent power struggle with Hezbollah and its allies.
Being conducted under a new law, this year's election will largely be decided by the voting in divided Christian districts. Aoun, a former army commander, faces Christian rivals in the shape of the Phalange party of former president Amin Gemayel and the Lebanese Forces of Samir Geagea.
The influential Christian Maronite Patriarch Nasrallah Boutros Sfeir on Saturday warned of "a threat to the Lebanese entity and its Arab identity" in remarks seen as a veiled attack on the Iran-backed Hezbollah.
Much of the campaigning has focused on the group's guerrilla army, which is stronger than the state's security forces.
Opponents say Hezbollah's weapons undermine the state, while the group and its allies see them as crucial to defending Lebanon from Israel.
As polls open at 7 a.m. (0400 GMT), some 50,000 members of the security forces are deploying to guard against violence, focusing on areas where competition is expected to be tightest. Thousands of soldiers fanned out at polling stations across the country.
There have been sporadic security incidents in the weeks leading up to the election. But tensions have mostly been kept in check by leaders whose rivalries pushed the country to the brink of civil war last year.
A thaw in ties between Saudi Arabia and Syria is widely credited with maintaining stability in Lebanon in recent months.
Around 200 international observers will be monitoring the vote.