The winners of the elections, who will inevitably be Shiites, could, of course, appoint Sunni representatives.

The 15 Sunni representatives took such a tough approach to the negotiations that several Shiite and Kurdish leaders said privately that there was no deal they would agree to.

In a news conference, Mr. Khalilzad, the American ambassador, told reporters he was "disappointed" by the Sunni representatives' decision to oppose the constitution.

Mr. Pachachi is favored to be the Sunni representative on the three-member presidency council that will head the interim government.

Sunni representatives rejected the offer.

His elevation is unlikely to impress restive Sunnis, who have long complained that the council's Sunni representatives do not adequately reflect the political views of their community.

"We've had a little fiasco in the National Assembly," said Sadoon al-Zubaidy, a Sunni representative who was on the constitutional committee.

"The dialogue is between Shia and Kurds, the Sunni representatives have been left in the shadows."

The original committee was made up of four Sunni representatives and four Shi'i representatives.

Mr. Mutlak, the Sunni representative, was the principal person in the meeting opposed to the expansion of regional autonomy, saying it could fragment the state.