BAGHDAD, Iraq — The Iraqi parliament accepted a final draft of a new constitution yesterday as top leaders from the nation's Sunni Muslim minority warned that the document could tear the country apart along sectarian lines.

With most of the Sunni leadership condemning the constitution, many in Iraq feared that minority's resistance will fuel civil and insurgent violence in Iraq and sabotage Bush administration plans for Iraq's transition to democracy.

President Bush acknowledged yesterday a split by Iraq's Sunnis, but downplayed it as a natural development in a nation of "free individuals living in a free society."

"Of course, there's disagreement," Bush said at his ranch in Crawford, Texas. "We're watching a political process unfold."

Bush predicted a rise in attacks by insurgents in advance of the country's Oct. 15 referendum vote on the constitution.

"Terrorists will become more desperate, more despicable and more vicious," he said, while expressing confidence Iraq would continue to move toward democracy.

Although the new constitution makes several concessions to Sunni concerns, it was brokered almost entirely by leaders of the nation's Shiite majority and Kurdish politicians.

None of the 15 Sunni representatives added to the committee that drafted the constitution agreed to sign the final document, and Shiite and Kurdish lawmakers chose yesterday not to put the charter up for a vote in parliament.

Chief among Iraqi fears is that the Sunni-led insurgency will step up recruiting in Sunni territories, already the base of guerrilla fighting, and that ordinary Sunnis will become more approving of insurgent attacks against both Shiite targets and the U.S. military.

In the political arena, Sunni leaders intend to campaign hard to get two-thirds of the voters in three provinces to reject the constitution in the October referendum.

If they succeed, the document will be scrapped and probably spark a backlash from Shiites and Kurds. If they fail, Sunnis will live under a system likely to alienate them further from the nation's governance.

Peter Galbraith, a former U.S. ambassador to Croatia and an adviser to the Kurds, said in Baghdad yesterday that the constitution and the coming referendum are Iraq's last chance to avoid fragmenting into Balkanlike states defined by ethnicity and religion.

"If it fails in the referendum, the next negotiations will be about independence," he said. "This constitution is the only thing that will hold this country together ... this is the last chance."

Sen. Joe Biden of Delaware, the ranking Democrat on the Senate Foreign Relations Committee, agreed.

"At the end of the day, if the Sunnis and that entire portion of the country opts out of this process, that's a formula for civil war," Biden said on ABC's "This Week."

The trouble came to a head when, after weeks of stalemate, Shiite and Kurdish politicians began meeting without the Sunnis to reach compromises on their own sticking points. They agreed on a draft last week and were prepared to present it to the legislature whether the Sunnis were on board or not.

Then, on Wednesday, President Bush called Abdul Aziz al-Hakim, the preeminent Shiite politician, and urged additional concessions to the Sunnis, according to Shiite politicians.

The Shiite camp was furious over Bush's intervention, but the Shiites and Kurds agreed to tweak two points: They made it easier to abolish the committee that restricts the participation of former members of Saddam Hussein's party — many of them Sunnis — in the government, and they agreed to leave unresolved for now the mechanisms by which the central government would relate to regional governments.

Late Friday, after the Sunnis rejected the changes as insignificant, the other parties decided to move on without them.

Some Sunni leaders said the joint drafting effort failed because the Bush administration decided that it was more important to make the mid-August deadline than to allow time to reach consensus. Sunnis on the drafting committee had sought a six-month extension to break impasses on key sections.

"The American administration doesn't care if there is consensus among the groups or not. All they care about is to say that they have succeeded in Iraq," said Nabil Mohammed Salim, a Sunni professor on the drafting committee.

While many disagreements among the groups focused on power-sharing and religious matters, the issue that brought discussions to a standstill was the role of Saddam Hussein's former Baath party.

For many Sunnis, Baathist ideology was a source of Arab nationalist pride before Saddam subverted it as a tool of oppression. For almost all Shiites and Kurds, however, it was the face of a regime that tortured and slaughtered thousands for nearly 30 years.

Shiite negotiators did agree to drop the word "party" from the section outlawing the "Saddam Baath party," leaving open the possibility that only Baathists connected with Saddam would be targeted by the Iraqi government.

Sunnis were unappeased. Many of them suspect that the Shiites, who swept January elections after a Sunni boycott, are bent on purging Baath members from all levels of government.

Jawad al-Maliki, a Shiite on the constitutional committee, said Sunnis poured all their anger into the issue. "Iraq cannot bear the return of this party, the political terrorism and killings and mass graves," he said. "Our [Sunni] brothers must understand that this issue was not targeting them in particular; it was against a party."

Celebrating the completion of the draft, Shiite and Kurdish leaders sidestepped questions on the Sunni outrage.

"This draft constitution was written by Iraqi hands, with their different classes, sects and religions," said Sheikh Homam Hamoodi, a Shiite cleric who led the drafting committee. "It's a constitution that guarantees freedom in all its forms ... a beautiful experiment."

After a news conference held on the front lawn of Iraqi President Jalal Talabani's home, where Kurdish and Shiite politicians clapped and hooted with joy, Sunni legislator Mishan al-Jubouri was asked if his presence was a sign of support for the document.

"This is not my constitution; I came just to see this show and cry," Jubouri said, adding that he thought the U.S. Embassy was pushing for such displays of sectarian unity because of worsening American sentiment about the war in Iraq. "I think Mr. Bush needs this show."

Los Angeles Times contributed to this report, as did Knight Ridder reporters Richard Chin, Huda Ahmed, Mohammed al Dulaimy, Alaa al Baldawy and Ahmed Mukhtar.