A Sunni Arab faction suspended participation Wednesday in the crafting of Iraq's constitution, and a Kurdish bloc asserted claim to hundreds of square miles of additional territory stretching south of Baghdad. The two moves presented fresh challenges to efforts to draft a document that proponents hope will help bring order to the chaotic country.

The Sunni faction launched its boycott to protest security conditions after gunmen on Tuesday killed one of 15 Sunni members of the constitution-writing committee. Initial reports that two members died in the attack turned out to be wrong.

U.S. diplomats were seen entering a meeting late Wednesday with the Sunnis who suspended participation in the committee. There was no immediate word on the outcome of the meeting, which appeared to reflect what the chairman of the constitution committee called the Americans' "big role" in keeping the Sunni minority involved in the process. Sunnis form the backbone of the insurgency; the interim government views their engagement in the constitution process as key to stabilizing the country.

The committee chairman, Humam Hammoudi, told reporters at a news conference Wednesday that the body remains on target to finish a draft of the constitution by an Aug. 15 deadline. But he and other committee members made clear that there was no agreement on some major issues, including the decentralized federal structure that some have urged. Some Sunnis fear such a structure could split the country into Kurdish, Shiite and Sunni enclaves.

Division remained, too, on seemingly small issues such as the country's official name.

"Federal and Islamic Republic of Iraq," Hammoudi, a member of the strongly religious Shiite Muslim coalition now leading Iraq, told reporters Wednesday.

"Federal Republic of Iraq," said Saadi Barzanchani, a member of Iraq's largely secular Kurdish minority and a committee member. "Once you say that a state is Islamic, you say that a state should pray, perform the hajj," Barzanchani said, referring to a pilgrimage to Mecca.

Iraq's interim government, created on April 28 after a national election, has a mandate to develop a constitution that will pass a referendum. The writing of the constitution in Baghdad's U.S.-created Green Zone is proceeding as insurgents stage daily bombings and ambushes across the country.

The latest suicide bombing killed at least 10 people Wednesday outside an army recruiting center at Baghdad's Muthanna airport. The center and its recruits have been the targets of repeated attacks. On July 10, a bomber killed 25 people there.

"We were separated, then one Iraqi soldier told us to gather and stand in a line," Thaer Falah, 27, a recruit, said in a hospital, where he lay with burns on his face and stomach. Other badly burned bombing victims screamed around him.

The bomber "was among us, and all that I remember is it was as if I were surrounded by fire, and then I did not see or hear anything until I was in the hospital," he said, as a nurse wiped the blood from his face.

Popular resentment and impatience with Prime Minister Ibrahim Jafari's interim government have surged in recent weeks in the face of such attacks, which also contribute to hours-long interruptions in electricity and water service in 120-plus-degree heat.

In the constitution negotiations, Kurds have pushed hard for a federal system, with strong regional governments. They have had broad autonomy from Baghdad since the Persian Gulf War of 1991, protected from Saddam Hussein's government by U.S. air power.

In recent months, Kurdish security forces have abducted hundreds of Arabs and members of the Turkmen minority in the city of Kirkuk and taken them to prisons in the Kurdish zone, according to U.S. government documents and interviews with families of the victims. Kurds hope to make the city and its reserves of petroleum part of an autonomous Kurdistan.

On Wednesday, some Kurdish leaders presented a redrawn map of Iraq with an enlarged Kurdistan. Reflecting long-standing land claims that are recognized only by the Kurds, the map pushes their territory hundreds of miles to the south. The farthest point included in the territory is the city of Jassan, about 75 miles southeast of Baghdad.

Barzanchani said Kurds wanted the map to be made part of the constitution, in an appendix.

Officials of both major political parties in the Kurdish zone backed the redrawing of Iraq's internal boundaries. "We shouldn't give up any Kurdish soil," said Abdul Ghani Ali Yahya, a spokesman for the Kurdistan Democratic Party.

It wasn't clear if the claims had any support from the top Kurdish national leaders, including President Jalal Talabani, who repeatedly has spoken against calls for Kurdish independence.

For now, the committee remains divided on questions of central authority. "There are enemies of federalism," Barzanchani said Wednesday. "Some oppose it because of ignorance and some intentionally because they don't want Iraq to be stable. We think federalism is a proper system for an ethnically and religiously diverse community like Iraq."

Federalism also is gaining support among some committee members from the Shiite majority. "Mass graves are only one of the results of the central system. Dictatorships are another," Qasim Dawood, a member from the heavily Shiite south, told reporters at the news conference.

Sunni Arabs have traditionally opposed the weakening of the central government.

Sunni committee member Mijbil Esa and an adviser were shot dead as they rode in a car through Baghdad. On Wednesday, a Sunni member of the constitution committee, Saleh Mutlaq, charged that the assassination was meant to silence an opponent of federalism.

Esa had told associates he felt threatened in recent days "from some parties in the government," Mutlaq said. Mutlaq refused to elaborate.

He and three or four other Sunnis suspended their participation in the drafting of the constitution, Mutlaq said. They wanted an investigation into the killing and better protection for surviving Sunni committee members before they would return.

Also Wednesday, the tribunal prosecuting former president Hussein dismissed nine staff members who it charged were former Baath Party members working to delay Hussein's trial.

"These people think that their presence in such places will convince some Iraqi people that Saddam will be back to power -- or at least they deceive themselves of that," said Talib Mhanna, a member of the committee charged with purging Hussein-era Baathists.

Judge Ammar Bakri, administrative director general of the trial, is among those likely to be dismissed next, Mhanna said in an interview.

Shiites in Iraq's new government have called for Hussein to be tried by the end of the year.

In another development, the U.S. military said that last week it captured three al Qaeda members linked to bombings in and around Baghdad. The three were associates of the man the military said was a chief al Qaeda organizer of bombings in Baghdad, Muhammad Rabi Hadi Jassir Dulaymi.

Special correspondents Bassam Sebti and Omar Fekeiki contributed to this report.