As another midnight deadline to complete a draft constitution without definitive agreement among Iraq's main factions, ruling Shiite Muslim parties said they would present a final version to the National Assembly this weekend with no further changes, even though it was rejected by several Sunni Arab leaders.

As some lawmakers said negotiations were continuing into the early hours of Saturday and others claimed an accord had been reached that many Sunnis would endorse, government spokesman Laith Kubba told al-Arabiya television that "consensus is almost impossible at this point."

"The draft should be put before the people," he said, referring to the nationwide referendum on the document that must be held by Oct. 15. Many Sunni Arab leaders have urged their followers to vote against the constitution, which can be rejected if two-thirds of the voters in at least three of Iraq's 18 provinces oppose it.

The completed document will be presented to the National Assembly on Saturday or Sunday with or without Sunni backing, Humam Hamoudi, a Shiite who is chairman of the constitution-writing committee, told the Associated Press.

Also Friday, the U.S. military said it launched multiple strikes with F-18 fighter jets against a house in the western town of Husaybah that local informants said was sheltering about 50 suspected insurgents from the group al Qaeda in Iraq. The military said the number of casualties had not been determined.

The highly politicized process of writing Iraq's constitution revealed and reinforced deep divisions among Iraq's Shiite and Sunni Arabs and ethnic Kurds, raising fears that disagreements could spiral into factional conflict.

In an attempt to foster consensus, an Aug. 15 deadline for completing a draft was postponed by one week and subsequently extended twice more. Friday's was the first deadline to pass without a statement granting more time.

In recent days, President Bush, who along with other U.S. officials had urged Iraqi leaders to complete their work on time, personally intervened by telephoning Abdul Aziz Hakim, leader of the largest Shiite political party, the Supreme Council for the Islamic Revolution in Iraq, to encourage conciliation with the Sunnis. U.S. and Iraqi officials have long maintained that inclusion of the Sunni Arabs, a once-dominant minority who now make up much of the violent insurgency, is a key to stability and the eventual withdrawal of American troops.

In Washington, a senior State Department official involved in Iraq policy said: "What we're witnessing is the endgame of this process. Events are moving in a positive direction. They're continuing to work these issues, but they're moving in the right direction."

Deliberations bogged down Friday over two issues that were as much about Iraq's past as its future: whether and how to bar former members of Saddam Hussein's Baath Party from political life, and how to devolve power from the federal government to autonomous regions that suffered greatly under Hussein's rule.

Shiites said they offered to eliminate language outlawing the Baath Party, whose top officials were mostly Sunnis, while retaining a ban on its "Saddamist" branch and symbols. They also offered to permit the National Assembly, by a majority vote, to eliminate the committee charged with removing former Baathist Party members from government service.

On federalism, or the ability of Iraq's provinces to form regional governments, Shiites said they proposed enshrining the principle of federalism in the constitution while leaving the details of how federal regions should be formed to future lawmakers. Some Shiites said they had agreed to have the constitution bar the formation of new regional governments for at least two years.

"This is the last offer we have. We cannot go back anymore," said Nabeel Mousawi, a member of the constitution committee from the ruling Shiite alliance. "If we keep fulfilling their demands, it would be better to go back to Saddam's government, because the alliance believes that the only benefit we got from the war was to get rid of the Baath Party and to gain federal states."

Sunnis, however, say that extending federalism beyond the existing Kurdish regional government in the north could lead to partition of the country. They strongly oppose a potential Shiite state in the south.

"What they have proposed will only create division and disturbance," said Saleh Mutlak, a Sunni member of the constitution committee. "People should reject this constitution."

Despite the dissenting voices, Kurdish and Shiite leaders said as broad an agreement as possible had been reached and largely dismissed the objections of Sunnis who they said did not truly represent their communities.

"I think for all intents and purposes we have a deal. We have a draft that cannot be improved upon," said Planning Minister Barham Salih, a Kurd. "No one could be entirely happy with what we have, but . . . many Sunnis expressed happiness."

As factional leaders huddled in Baghdad's fortified Green Zone for talks, large crowds took to the streets across the country.

More than 3,000 demonstrators, many of them Sunnis opposed to the constitution, gathered in Baqubah, north of the capital. Marchers chanted Baath Party slogans and carried large posters of Hussein.

In the northern city of Kirkuk, police officers and Iraqi soldiers joined about 2,000 demonstrators bearing banners that read "The Baathists are loyal Iraqis" and "No to federalism."

The largest demonstrations of the day were inspired by the influential Shiite cleric Moqtada Sadr, who has yet to make public his opinion on the constitution but whose stated opposition to federalism mirrors that of many Sunnis.

About 20,000 followers of Sadr marched in their stronghold of Sadr City, a sprawling slum in eastern Baghdad.

The movement convened other demonstrations in several cities in southern Iraq, protesting a dearth of social services.

Correspondent Anthony Shadid and special correspondents Naseer Nouri and Bassam Sebti in Baghdad, special correspondent Saad Sarhan in Najaf, and staff writers Robin Wright and Mike Allen in Washington contributed to this report.