US President George W. Bush has appealed for concessions to be made to Sunni Arabs to win their support for a new constitution in Iraq.
US officials have also appealed to the country's powerful Shia clergy, including Grand Ayatollah Ali al-Sistani, to help resolve the standoff, said Ali al-Adeeb, a Shia member of the committee drafting the charter.
State Department spokesman Sean McCormack
Shia negotiators agreed to study suggested changes to the document today after parliament speaker Hajim al-Hassani announced that officials would try again to reach unanimity after the latest deadline passed at midnight last night.
A Sunni negotiator has blamed Kurds, citing their "intransigence" over the issue of federalism, which the Sunnis oppose.
Several Shia negotiators, expressing frustration with the continued delays, said yesterday there was no need for unanimity or a parliament vote and that the draft approved Monday by them and the Kurds should go to voters in an October 15th referendum without further changes.
The United States, hoping to lure Sunni Arabs away from the insurgency, had pressed the Shias and Kurds to accept 15 unelected Sunni negotiators on the drafting committee last spring to ensure that the community was represented. Sunni Arabs form the core of the insurgency.
Some 5,000 people, some carrying Saddam's picture, rallied in the mostly Sunni city of Baqouba today to protest at the draft constitution. The rally was organised by the Iraqi National Dialogue Council, a Sunni group whose spokesman is a constitution negotiator.
Parliament speaker Hajim al-Hassani, a Sunni who was elected on the mostly Sunni ticket headed by former President Ghazi al-Yawer, agreed that the law does not require a parliament vote.
Sunni Arabs said federalism, including the demand for a Shia mini-state in the south, remained the major obstacle. But they said the Kurds were unwilling to budge on that issue to protect their own self-ruled region in three northern provinces.
Sunni Arabs fear that federalism will lead to the breakup of the country and deprive them of oil wealth, concentrated in the Shia south and the north - much of it in areas the Kurds rule or want to incorporate.
But Kurds and the majority Shia bitterly recall decades of oppression at the hands of Saddam's Sunni-dominated dictatorship. They believe federalism is the best way to prevent a new dictator.
The Bush administration expressed optimism an agreement would be reached.
"I think if Iraqi leaders say that they need a few days more to complete a historic document that will lay a foundation for a new and free Iraq, I think that that is certainly understandable," State Department spokesman Sean McCormack said after the delay was announced.
Although the constitution requires only a simple majority in the referendum, if two-thirds of the voters in any three of Iraq's 18 provinces vote against it, the charter will be defeated.
Sunni Arabs make up about 20 per cent of the national population but form the majority in at least four provinces. Sunni clerics have begun urging their followers to vote down the charter in the referendum if Sunni interests are not served.
If voters reject the constitution, parliament will be dissolved and elections held by mid December to form a new one. The new parliament would then start drafting a new constitution.