The 128 members of the Shia alliance who won parliament seats in the December 15 balloting, gathered on Saturday in Baghdad to choose their candidate for prime minister.
But the vote was postponed for a day at the request of Shia leader Muqtada al-Sadr's faction because of differences with another group, according to Shias who attended the meeting.
The Shia officials, speaking on condition of anonymity because of the sensitivity of the negotiations, said al-Sadr's faction was leaning towards Ibrahim al-Jaafari , the current prime minister, as its choice to lead the new government.
But another Shia group, Fadhila, was having second thoughts about al-Jaafari, and al-Sadr's lieutenants wanted time to confer with the other bloc's leadership before the issue went to a vote, the officials said.
All that could strengthen the position of the other major candidate, Adil Abdul-Mahdi, the French-educated vice president and former finance minister who is backed by the Supreme Council for the Islamic Revolution in Iraq (SCIRI).
Difficult to predict
Some Shia lawmakers cautioned that the situation was fluid and the outcome difficult to predict.
The alliance's choice is assured of the prime ministership because Shia parties won the biggest number of parliament seats.
However, the alliance is not a cohesive organisation but is made up of several Shia parties and factions, each with its own programmes and visions for Iraq.
Abdul Mahdi (L), a vice president,
enjoys the support of SCIRI
Within the alliance, the supreme council, led by Abdul-Aziz al-Hakim, and its military wing the Badr organisation together hold 30 seats.
The winner needs a simple majority among the 128 parliamentarians. Al-Jaafari was meeting late Saturday with alliance parliamentarians not allied with any of the major factions in hopes of winning their support.
Al-Sadr and an allied group control another 30, and the two wings of al-Jaafari's Dawa party have 25. The rest are shared by Fahdila and independents.
However, one independent Shia lawmaker said his fellow independents held a straw vote on Saturday night and Abdul-Mahdi won, although he refused to say by how much.
The lawmaker, speaking on condition of anonymity because of the straw vote was supposed to be confidential, said it appeared unlikely the alliance could agree unanimously on a prime minister and a vote Sunday would be necessary.
After parliament convenes within two weeks, members must choose a president, a largely ceremonial position.
The president then designates the alliance's choice as the new prime minister, who has 30 days to appoint a cabinet and win majority approval in the legislature. The entire process could take months.
Once the alliance settles on a prime minister, it will begin talks in earnest with parties representing Sunni Arabs, Kurds, secularists and others to try to form a broad-based government, which the US hopes can calm the the uprising so American and other foreign troops can begin heading home.
The US hopes the Shia will offer key posts to Sunni Arabs, the backbone of the anti-US presence opposition, in hopes of encouraging them to support the government.
SCIRI, led by al-Hakim, is a key
member of the Shia alliance
Two Sunni Arab alliances won 55 seats in December, a threefold increase in Sunni Arab representation over the outgoing parliament.
But the talks will take place amid rising tensions between Sunni and Shia Arabs after months of reprisal killings and amid the raging Sunni-led armed uprising.
Meanwhile, US officials are trying to reach out to Sunni Arabs tired of the violence, including some tribal leaders in strife-torn areas such as Anbar province.