The Shiite-Kurdish faction that runs the country said it had come up with a constitution that would work - but fundamentally transform Iraq from the highly centralized state of Saddam Hussein into a loose federation of Kurds, Shiites and Sunni Arabs.

However, the Sunni Arab minority - which had dominated Iraqi society for centuries and whose support is key to stopping the insurgency - flatly refused to go along. It forced another delay in the vote and threw down the gauntlet, saying it won't agree to any constitution it doesn't like.

The parliament speaker said the sides needed three more days to hammer out a compromise.

Speaking to veterans Monday in Salt Lake City, President Bush acknowledged the difficulties the Iraqis face.

"Producing a constitution is a difficult process that involves debate and compromise; we know this from our own history," Bush said. "The Constitution our founders produced has been amended many times over. So Americans understand the challenges facing the framers of Iraq's new constitution."

Bush said those working on the document "will produce a constitution that reflects the values and traditions of the Iraqi people," noting that the constitution would probably change over time.

In Iraq, U.S. Ambassador Zalmay Khalilzad said the three major issues blocking a deal were federalism, purging Saddam's Baath Party and whether some of the officers of the assembly should be elected by a majority or two-thirds vote.

But Saleh al-Mutlaq, one of four top Sunni Arab negotiators, said more than 20 issues still divide the sides. Apart from federalism and power-sharing, he cited how the constitution spoke of Iraq's national identity as ''part of the Islamic world'' rather than the Arab world - a concession to the non-Arab Kurds.

''This constitution is full of land mines that would explode on Iraqis. This constitution will divide the country,'' al-Mutlaq said.

The numerous remaining issues referred to by al-Mutlaq cast doubt on whether the Iraqis would be able to finish the document within a few days since the various groups have widely differing positions. Repeated delays are a deep embarrassment for the Bush administration at a time of growing misgivings within the United States over the mission in Iraq.

Washington had applied enormous pressure on the Iraqis to meet the original Aug. 15 deadline but parliament instead had to grant a week's extension, which they again failed to meet.

The U.S. military said two U.S. soldiers from Task Force Liberty were killed Monday by a roadside bomb during a combat patrol north of Baghdad, and two more soldiers died Sunday when their vehicle overturned during a military operation near Tal Afar. At least 1,870 U.S. troops have died since the Iraq war started in 2003, according to an Associated Press count.

---

Tribune reporter Matthew D. LaPlante contributed to this story.