The 15 members of the Sunni panel said they rejected the document because of disagreements over such issues as federalism, Iraq's identity and references to Saddam Hussein's Sunni-dominated Baath Party.
Sunni Arab negotiators also said in a joint statement that they had asked the United Nations and Arab League to intervene. The country's parliament speaker, a Sunni Arab who was not on the negotiating panel, said he had "some reservations" about the draft, including "too much religion" and curbs on women's rights, and thought Shiites should have offered more concessions to the Sunnis.
And the country's Sunni vice president, former President Ghazi al-Yawer, did not appear at a ceremony with senior leaders marking the end of the drafting process. Asked why al-Yawer was absent, President Jalal Talabani said, "he's sick," prompting peels of laughter from officials, including Deputy Prime Minister Ahmad Chalabi, a Shiite.
The document, which included last-minute changes aimed at easing Sunni concerns, was read to lawmakers. It was not put to a vote in the assembly, where the Shiite-Kurdish bloc has an overwhelming majority.
"The constitution is left to our people to approve or reject it," Talabani, a Kurd, told the ceremony. "I hope that our people will accept it despite some flaws."
Talabani acknowledged that the Sunni Arabs had objections to the draft "but everybody had reservations. This is part of democracy. If the people do not approve it, we will draft another constitution."
CBS News Correspondent Lara Logan reports that the Sunni speaker of Iraq's parliament denied the negotiations had divided the country but admitted it was dangerous not to have the Sunnis on board.
"It will certainly give the insurgency more chance to do whatever they want to do and the terrorists will benefit from that," Iraqi Parliament Speaker Hajim al-Hassani told Logan.
Prime Minister Ibrahim al-Jaafari, a Shiite, said no constitution anywhere in the world enjoyed universal acceptance, and "I personally have reservations on some points and so do the Kurds." But he urged Iraqis to support the draft in the referendum.
Hajim al-Hassani, the Sunni Arab speaker of the legislature, was not present, but deputy speaker Hussain al-Shahristani, a Shiite, told reporters that the speaker agreed with all parts of the draft and had "other appointments."
Al-Hassani played a major role in the final negotiations on the charter, which now goes to the Iraqi people in an Oct. 15 referendum. Later, after a ceremony with Talabani marking the end of the drafting process, al-Hassani said the constitution had "too much religion" and curbs on women's rights.
He also said the Shiites and Kurds should have "been more generous" to win over the Sunnis and "in the long run I do not think that is going to be on their side."
Technically, no vote was required by parliament. At one time, officials wanted a vote as an affirmation of unity between the Shiites, Sunnis and Kurds, but that idea was shelved because of Sunni objections to the document and repeated delays in finalizing the draft.
Sheik Humam Hammoudi, chairman of the drafting committee, said the constitution "guarantees freedoms and equalizes between everyone, women and men and different ethnic groups and respects the ideologies of this nation and the religion of this society."
But the 15-member Sunni negotiating team immediately rejected the document, which it called "illegitimate."
"We call upon the Arab League, the United Nations and international organizations to intervene so that this document is not passed and so that the clear defect in it is corrected," said the statement read by Abdul-Nasser al-Janabi.
A top Sunni negotiator, Saleh al-Mutlaq, told Alhurra Television that all opponents of the constitution will hold a conference to decide their next move. He gave no date.
"Now we will move to a general conference that includes all groups that did not take part in the (Jan. 30) elections to take a decision," he told the U.S.-funded station.
Al-Mutlaq said earlier the Sunni negotiators would not sign off on the final draft because of objections to provisions that allegedly threaten Iraqi unity, particularly federalism, and fail to affirm the country's Arab identity. The draft refers to Iraq as an Islamic, but not Arab, country as the Sunnis demanded.
"I think if this constitution passes as it is, it will worsen everything in the country," he said.
At the same time, al-Mutlaq urged all Iraqis to refrain from violence.
Another top Sunni negotiator, Mohammed Abed-Rabbou, said the Sunni team refused to endorse the draft because "points of disagreement" were not amended, including proposals to transform Iraq into a federated country and references to Saddam's party.
The comments set the stage for a bitter political battle before the October referendum, when Iraqis will decide whether to accept or reject the document. Five million copies of the constitution will be circulated nationwide in food allotments each Iraqi family receives monthly from the government.
Sunnis account for only 20 percent of Iraq's estimated 27 million people, but they are in a strong position to derail the 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.
After two months of talks, negotiators for the Shiite-Kurd bloc and the Sunnis remained divided over such fundamental issues as:
Whether Iraq should be turned into a federal state or decentralized by granting more power to provincial authorities;
How the country's oil wealth will be divided;
Whether Baath Party members should be purged from government; and
Whether Iraq will be considered an Arab or Islamic nation.
The deadlock came despite frantic U.S. efforts to secure a political consensus that hopefully would deliver a massive vote for the charter, taking the steam out of the Sunni-led insurgency and enabling a withdrawal of U.S. troops to start next year.
In other developments:
Ahmed Abdul Ghafour al-Samarrai, head of the government's Sunni Endowments, said the bodies "are believed to be for people from (Baghdad's northern neighborhood of) Hurriyah and they belong to the Sunni sect." The cleric did not give further details.
If true, the killings are likely to heighten sectarian tensions. Both Sunnis and Shiites have accused one another of involvement in "death squad" assassinations of members of the rival sect.
All the men were shot in the head, and some were handcuffed. The bodies were discovered near Badrah, southeast of Baghdad.