BAGHDAD, Iraq – Iraqi officials finished the new constitution yesterday, but it was rejected by Sunni Arab negotiators, a blow to the Bush administration’s strategy to lure members of the minority away from the insurgency and hasten the day American troops can go home.

The absence of Sunni Arab endorsement, after more than two months of intensive negotiation, raised fears of more violence and set the stage for a bitter political fight ahead of an October 15 nationwide referendum on the document.

A political battle along religious and ethnic lines threatened to sharpen communal divisions at a time when relations among the Shiites, Sunni Arabs, and Kurds appear to be worsening.

Sunni negotiators delivered their rejection in a joint statement shortly after the draft was submitted to Parliament. They branded the final version as “illegitimate” and asked the Arab League, the United Nations, and “international organizations” to intervene “so that this document is not passed.”

Such intervention is unlikely, and no further amendments to the draft are possible under the law, a legal expert on the drafting committee, Hussein Addab, said.

In Crawford, Texas, President Bush expressed disappointment that the Sunnis did not sign on but pinned his hopes on the referendum. “Some Sunnis have expressed reservations about various provisions in the constitution, and that’s their right as free individuals in a free society,” Mr. Bush told reporters.

He said the referendum was a chance for Iraqis to “set the foundation for a permanent Iraqi government.”

But the depth of disillusionment over the charter in the Sunni establishment extended beyond the 15 negotiators, who were appointed to the constitutional committee in June under American pressure.

The country’s Sunni vice president, Ghazi al-Yawer, didn’t show up at a ceremony yesterday marking completion of the document. When President Talabani said that Mr. al-Yawer was ill, senior government officials including Deputy Prime Minister Ahmad Chalabi howled with laughter.

“The constitution is left to our people to approve or reject it,” Mr. Talabani, a Kurd, said. “I hope that our people will accept it despite some flaws.”

A top Sunni who did attend the ceremony, the Parliament speaker, Hajim al-Hassani, said he thought the final document contained “too much religion” and too little protection of women’s rights.

A spokesman of a leading insurgent group, the Islamic Army in Iraq, Ibrahim al-Shammari, said on Al-Jazeera television that the constitution “drafted under the supervision of the occupiers” would divide Iraq and benefit Israel.

Major deal-breaker issues included federalism, Iraq’s identity in the Arab world, and references to Saddam Hussein’s Sunni-dominated Baath Party.

Sunnis fear federalism would lead to the breakup of the country into a Kurdish north and Shiite south. They believe such a move would deprive Sunnis of Iraq’s vast oil wealth concentrated at the opposite ends of the country and open the door to Iranian influence in the Shiite south.

Many key Shiite leaders took refuge in Shiite-dominated Iran during Saddam’s rule. The constitution identifies Iraq as an Islamic – but not an Arab – country, a concession to the Kurds and other non-Arab minorities.

Sunnis also wanted no reference to Saddam’s party, fearing that would lead to widespread purges of Sunnis from government jobs and public life.

The parliament speaker, who was not part of the Sunni negotiating team, said the Shiites and Kurds should have been more accommodating to the minority.

Although Sunnis account for only 20% of Iraq’s estimated 27 million people, they still can derail the constitution in the referendum due to a concession made to the Kurds in the 2004 interim constitution. If two-thirds of voters in any three provinces reject the charter, the constitution will be defeated. Sunnis have the majority in at least four provinces.

Defeat of the constitution would force new elections for a parliament that would begin the drafting process from scratch. If the constitution is approved, elections for a fully constitutional parliament will be held in December.

For America, one of the few silver linings in the bitter constitutional debate is to convince many Sunnis that they made a profound mistake by boycotting the January 30 election and should take part in the political process. So few Sunnis were elected that their constitution negotiators had to be appointed, reducing their influence on the committee.

Sunni clerics, who were at the forefront of the boycott campaign, are now urging their followers to register for the referendum and the December national election – although against the constitution.