"We reject Jaafari because we believe that Iraq needs a government of national unity and new faces," said Barhem Saleh, planning minister and a close aide to President Jalal Talabani, in an appeal to reclusive Shi'ite cleric Ayatollah Ali al-Sistani.
Mr Talabani, who on Sunday predicted the parliament elected in December would be able to meet in a week after two-and-a-half months of deadlock, dispatched Mr Saleh to meet Ayatollah Sistani to explain Kurd and Sunni opposition to Mr Jaafari.
Mr Saleh said Sistani heard "our arguments and underlined the need for continuing dialogues with other Iraqi factions", after his surprise visit to the southern holy city of Najaf to meet the revered cleric.
Kurds, Sunnis and secular political factions of Iraq oppose Mr Jaafari's candidacy, saying he had failed to curb the raging insurgency during his term.
Mr Saleh also met with radical Shi'ite cleric Moqtada Sadr, one of the Mr Jaafari's main backers.
He said Sadr insisted on national unity, however vowed to continue supporting Mr Jaafari.
The prime minister was picked by his ruling religious-based alliance by just one vote, indicating deep internal divisions.
The opposing Kurdish group has 53 seats in the new 275-seat parliament, the Sunni National Concord Front has 44, and the list of former premier Iyad Allawi controls 25.
The Shi'ite Alliance is the largest block with 128 seats.
Violence kills nine
In violence over the past 24 hours, at least nine people were killed, including five gunned down in separate attacks on a Shi'ite and a Sunni mosque.
Attacks on the Sunni community have multiplied since the February 22 bombing of a revered Shi'ite shrine, sparking fears of an all-out sectarian war.
Two Iraqi soldiers were also killed by gunmen who fired on their vehicle in Saddam Hussein's hometown of Tikrit, while police said the bodies of three men, two of them Shi'ites, were discovered in Nabai, 60 km north-east of the capital.
Iraqi state television said army forces had foiled an insurgent attack on a major Shi'ite shrine in northern Baghdad.
Meanwhile, the US military dismissed reports that foreign troops would leave Iraq by early next year.
Two British newspapers, the Sunday Telegraph and Sunday Mirror, quoted unnamed senior British Army sources as saying the coalition intended to reduce its presence on the ground over the next 12 months, while withdrawing forces into bases.
Later, the coalition would withdraw all remaining troops simultaneously.
The papers said Washington and London believe their military presence is now counter-productive as foreign forces are increasingly viewed as occupation troops, even though they remain at the Iraqi government's request.