Iraq's ruling coalition agreed a new constitution last night but the deal excluded Sunni Arabs, a momentous gamble which could divide rather than unite the country.
Shia and Kurdish leaders broke a deadlock over federalism and the role of Islam with a text that appeared to override Sunni objections. It was due to be presented to the national assembly shortly before a midnight deadline.
It was unclear if the assembly would approve it on time or vote to extend the deadline.
Negotiators hailed the document as a historic compromise that would shore up the political process and forge a social contract between the country's ethnic and sectarian groups.
A leaked extract defined Iraq 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.
"Thank God we have finished all the details related to the agreement," said Jawad al-Maliki, a leading member of the Shia delegation.
A precise definition of federalism was believed to have been deferred to allay Sunni concerns that regional autonomy would allow Kurds in the north and Shias in the south to form their own states and break up Iraq.
However, within minutes of its announcement some Sunni delegates rejected the draft as the work of "foundering fathers". They said Sunnis 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 the charter could lead to disintegration and civil war.
Shias and Kurds, partners in government and dominant in the 275-seat assembly, said they still hoped to convince Sunni delegates to support the draft before presenting it to the assembly.
That appeared unlikely and Mr Maliki said there would be no extension of the midnight deadline. "This draft will be offered and read and be voted on."
If approved, the constitution will be submitted to voters in a referendum on October 15th which, if passed, will pave the way for elections in December. The US drove this ambitious timetable, arguing that political progress would take the sting out of the insurgency.
American diplomats lobbied fiercely for a deal in what was seen as an effort to help President Bush quell criticism at home. But last night's agreement could backfire on Washington. Unless Sunnis are persuaded to support it, the referendum campaign could turn into a bitter political battle waged along sectarian and ethnic lines.