Baghdad - Iraq's ruling coalition submitted a new constitution to parliament last night but delayed a vote for three days to try to win over Sunni Arabs who said it could lead to civil war.

Shia and Kurdish leaders said they had reached a compromise between themselves and delivered a thinly veiled ultimatum to the Sunni minority to sign up to the deal by Thursday or retreat deeper into the political wilderness.

The document was submitted eight minutes before midnight, meeting a deadline mandated by the current constitution, but then withdrawn to give negotiators a last chance to forge consensus.

"Today we received a draft of the constitution but there are some points that are outstanding and need to be addressed in the next three days," said the speaker, Hachim al-Hassani. "There should be consensus so the constitution is acceptable to all."

Bringing the Sunnis on board has been billed as a crucial step to weakening the Sunni-driven insurgency. The prospects of reaching a consensus appeared bleak, with Sunni delegates complaining that their objections to federalism had been ignored.

Two other sticking points to be resolved were the division of powers between the president, the parliament and the cabinet, and so-called de-Ba'athification, the extent to which former members of Saddam Hussein's regime should be purged in the new Iraq.

Shias and Kurds appeared to have resolved other outstanding issues however. Iraq is to be defined as a federal republic which would combine the principles of Islam with human rights and democracy. Oil and other natural wealth would be shared "according to the needs" of the central government and the provinces.

A precise definition of federalism was believed to have been deferred to allay Sunni concerns that would allow Kurds in the north and Shias in the south to form their own states and break up Iraq.

However even before its unveiling some Sunni delegates rejected the draft, saying they were sidelined in negotiations and misled that there would be no deal without consensus.

"We reject the political process as it is now," said a spokesman, Salah al-Mutlik. "It will put us far from reconciliation and without reconciliation in this country we cannot advance." Soha Allawi, another Sunni member of the drafting committee, said: "We will campaign ... to tell both Sunnis and Shias to reject the constitution, which has elements that will lead to the break-up of Iraq and civil war,"

Once approved by parliament, which is dominated by Shias and Kurds, the constitution will be submitted to voters in a referendum on October 15 which, if passed, will pave the way for elections in December.The US drove this ambitious timetable, arguing political progress would take the sting out of the insurgency.

US diplomats lobbied for a deal on the constitution in what was seen as an effort to help President George Bush quell domestic criticism of US involvement in Iraq.

Speaking to war veterans in Utah, Mr Bush welcomed the news from Baghdad. "Iraq's leaders are once again defying the terrorists and the pessimists by completing work on a democratic constitution," said President Bush. "The establishment of a democratic constitution will be a landmark event in the history of Iraq and the history of the Middle East."

But unless Sunnis are persuaded to support it the referendum campaign could turn into a political battle along sectarian and ethnic lines.

Sunnis, a dominant minority under Saddam, have felt alienated since the 2003 US-led invasion and largely boycotted January's election, saying it lacked legitimacy while foreign troops were in the country.

But this time clerics, politicians and even some insurgent groups want Sunnis to vote and registration centres have sprouted in strongholds such as Ramadi and Falluja.