Iraqi factional leaders failed to meet Monday's deadline for drafting a constitution in an often-rancorous debate that appeared to have widened rifts among Shiite, Sunni, Kurdish and secular groups.

Unable to resolve differences on such major issues as the role of religion by the midnight deadline, political leaders turned to Iraq's transitional parliament for a one-week extension, winning unanimous agreement with just 23 minutes to spare. The United States had pushed the deadline hard as it eyed troop withdrawals.

Iraqi officials presented the extension as a success. They smiled and shook hands among themselves and with U.S. Ambassador Zalmay Khalilzad, who strolled on the floor of parliament ahead of the late-night vote.

"This to my mind is real democracy, and proves to the world that Iraq is writing its own constitution," Hachim Hasani, Chairman of the National Assembly, told members of parliament.

"Efforts have been made to reach agreements, but this is a historic issue that needs more study," President Jalal Talabani told lawmakers. "We need more time."

Political leaders had promised constitutional delegates they would reach accord if they had the extra week, said Mahmoud Othman, a Kurdish delegate to the country's constitutional committee. "I hope they will achieve that."

The insurgency opposed to Iraq's U.S.-backed government made its own voice heard before the vote, sending at least two mortar rounds in the direction of the National Assembly late Monday night. Although the booms resonated in the center of Baghdad, the U.S. military said no damage or injuries were reported in the concrete-walled Green Zone, where the assembly meets.

U.S. officials had pressed openly and strenuously for Iraq to make the deadline, highlighted by Defense Secretary Donald H. Rumsfeld's late-July trip to Iraq, during which he reminded Iraqi leaders of the daily U.S. military deaths here. Rumsfeld's words came ahead of insurgent bombings and ambushes that made the first week of August one of the bloodiest weeks of the war for American forces.

Iraq's national security adviser, Mowaffak Rubaie, said Monday he still expected U.S. military strength to be below 100,000 troops by early spring. About 138,000 American troops are now in Iraq.

Pushed by Washington, Iraqi leaders this month shifted much of the negotiation from parliament's appointed constitutional committee to leaders of Iraq's main political factions. In addition, Khalilzad sat in on the final days of talks and presented political leaders with U.S. proposals for the constitution, according to Iraqi constitutional delegates and other sources close to the talks.

Even so, none of the major sticking points appeared to have been resolved, and new ones emerged in the last days of the talks.

With hopes fading by early Monday, Western officials were pointing to interpretations of the country's interim, U.S.-written charter that they said would technically allow more time for the drafting. Delegates were presented with two versions of a draft constitution, one from Hasani, the parliamentary speaker, and one from constitutional committee Chairman Humam Hamoudi. Neither managed to close the gaps.

While political leaders haggled in a final try Monday evening, repeatedly delaying the convening of the National Assembly to approve the document, bored assembly members lounged and snapped pictures of each other with cell phone cameras. State television, poised to air the historic National Assembly session, instead broadcast seldom-seen footage of torture and executions carried out by the government of President Saddam Hussein.

The key issues dividing the drafters included federalism and the desire by Kurds to formalize the autonomy in place in northern Iraq since the 1991 Persian Gulf War. Many Kurdish leaders expanded the demand to include, at a minimum, constitutional recognition of the Kurds' right to independence should they choose it. Opposition to a separate Kurdistan by neighboring nations, however, makes such a break practically impossible.

"There will be no constitution" with Kurdish self-determination, warned Jalaladeen Sagheer, a constitutional committee member, Shiite Muslim cleric and member of the country's largest political party, the Supreme Council for the Islamic Revolution in Iraq. "It shall not pass."

At the same time, a split emerged among Shiite blocs, with the Supreme Council calling for the creation of what would be an oil-rich, Shiite-led superstate in the south over the objections of the Dawa party, the political organization of Prime Minister Ibrahim Jafari.

Sunni Arab delegates opposed federalism for the largely Shiite south, saying it would split Iraq and leave the Sunni minority with an impoverished substate in the west and central parts of the country.

Politicians were also divided over how great a role Islamic law should have in the constitution. A secular female delegate, Raja Khuzae, said an agreement had been reached that would allow Iraqis an alternative to religious law in matters such as marriage and divorce. Other delegates disagreed.

"In the end, the differences are so big and so wide we could not reach an agreement," said Saleh Mutlak, the most outspoken Sunni participant in the talks.

"They postponed the date because they want to agree upon everything, so the whole constitution is delayed," Mutlak said. "Practically, it is probably not enough time, but we hope everybody works hard to achieve it."

Iraq's interim charter gave the National Assembly until Aug. 15 to write the draft of a permanent constitution.

Iraqis were to vote on the document on Oct. 15 and then elect a full-term government on Dec. 15.

Under terms of the interim charter, if the National Assembly failed to meet the Aug. 15 deadline, it was to dissolve and elections were to be held for a new parliament that would try again. The literal 11th-hour vote Monday night -- technically an amendment to the interim constitution -- sidestepped that provision.

New elections could benefit Sunni Arabs, most of whom boycotted the January elections that seated the current assembly, leaving them with little clout in the constitutional debate. Sunni leaders are now encouraging participation in the next vote.

Kurdish and Shiite delegates accuse Sunni counterparts of holding out in the constitutional talks in hopes of forcing new elections, and warn that the tactic could result in the constitution being approved without Sunni delegates' approval.

Ultimately, "maybe Arab Sunnis will not be on board with us," said Othman, the Kurdish delegate.

Correspondent Jonathan Finer and special correspondents Khalid Saffar and Naseer Nouri contributed to this report.

Iraqi National Assembly members vote unanimously for a seven-day extension for writing a draft constitution, sidestepping a provision in the interim charter calling for dissolving parliament and holding new elections if the deadline was missed. Delegates remained divided on many issues.