The document was to have been signed on Friday, but objections by five Shia members of the US-appointed Governing Council forced an embarrassing postponement of the ceremony.
Council sources said the main point of contention was a clause that could allow Kurds to veto a permanent constitution if it did not address their demands for autonomy.
They said the dissenters were following instructions from Iraq's most revered Shia spiritual leader, Ayat Allah Ali al-Sistani, who objected to giving minorities veto power and wanted to ensure the Shia had political power.
In a statement issued early on Saturday, the council said there was "widespread consensus" on the document and there had been "constructive dialogue ... regarding an important sensitive issue".
"The council will reconvene on Monday 8 March to finalise the issue and sign the law," it said. Council sources said earlier that informal consultations would be held on Saturday and Sunday, before formal talks on Monday at 10am (07:00 GMT).
The White House played down the postponement as a technical setback, and said it still planned to hand sovereignty back to Iraqis on 30 June.
"The council will reconvene on Monday,
8 March, to finalise the issue and sign the law"
Iraq Governing Council
"You're seeing democracy in action," White House spokesman Scott McClellan said. "The important thing is that Iraqi leaders are able to freely discuss these issues with one another and do so publicly."
One Kurdish source close to the negotiations indicated the standoff would encourage Kurds - whose leaders say they are holding back popular demands for the maximum amount of autonomy - to hold a referendum on self-rule in northern Iraq.
The interim constitution was agreed on last Monday but the signing ceremony, set for Wednesday, was postponed to Friday after bomb attacks on Shia worshippers killed 181 people - and abruptly called off on Friday afternoon.
Dissenters are said to follow
orders from Ayat Allah Sistani
Hamid al-Bayati, of the Supreme Council for the Islamic Revolution in Iraq (SCIRI), said Shia objections centred on a clause on a referendum due to be held next year to approve a permanent constitution once it had been drawn up.
The clause states that even if a majority of Iraqis approves the constitution, it can be vetoed if two-thirds of voters in three provinces reject it. The clause was inserted by the Kurds, who run three provinces in northern Iraq and want to be able to veto any attempt to rein in their considerable autonomy.
Kurdish council member Mahmud Uthman said the Shia had objected to the clause on the ground that it enabled a minority to impose its will on the majority.
The Shia, unhappy with some aspects of the interim constitution, want to ensure the permanent document is more in line with their views, a Kurdish source close to the talks said.
Long oppressed by former President Saddam Hussein, Iraq's Shia are eager to exert political influence equal to their numbers - about 53% of the population.