The talks stalled on Wednesday after the Shia-led bloc of Prime Minister Ibrahim Jaafari insisted he should take control of the interior ministry.
Sunni Arab parties objected to the proposal and insisted a deputy prime minister should be given the ministry.
The three-month delay in forming a government is thought to have played a part in the recent upsurge in violence.
Many hundreds of Iraqis have died since last month's bombing of the al-Askari shrine in Samarra, one of Shia Islam's holiest.
On Friday, one of Iraq's most revered Shia clerics, Grand Ayatollah Bashir al-Najafi, called for a government to be formed as soon as possible to help quell the sectarian bloodshed.
"We warn all the politicians chasing after ministries and looting the country's wealth about the terrible consequences the country is facing," he said.
'Sectarian ambassador'
The coalition talks came a day after Mr Jaafari defended his right to stay in office and warned the US not to interfere in his country's politics.
On Tuesday, Iraqi politicians said US ambassador Zalmay Khalilzad had told them the US did not want Mr Jaafari to remain PM.
Another senior Shia cleric also criticised Mr Khalilzad, saying the ambassador was "giving political support to those parties who provide political cover for terrorists".
In a statement read out at mosques during Friday prayers, Ayatollah Mohammed al-Yaqoubi said Washington had underestimated the conflict between Iraq's Shia majority and its once dominant Sunni Arab minority.
"They are either misled by reports, which lack objectivity and credibility, submitted to the United States by their sectarian ambassador to Iraq... or they are denying this fact," he said.
"[The US] should not yield to terrorist blackmail and should not be deluded or misled by spiteful sectarians. It should replace its ambassador to Iraq if it wants to protect itself from further failures."