More-secular Sunnis and Kurds have backed changing that wording to the "agreed-upon" principles of Islam -- thereby greatly limiting the myriad Islamic rules that could be applied to laws. The groups had appeared sanguine about prospects of winning such a concession, but early Saturday they said they had failed.
"You try and put these phrases in, it creates a theocracy, and people don't want this," one negotiator said, speaking by telephone and on condition of anonymity. "Nobody could bring a beer here, nobody could go in the streets without a scarf. Did America want that?"
Officials said U.S. Ambassador Zalmay Khalilzad, who has been an active broker in the talks, had supported the stricter, Shiite-led position on the role of Islam. Khalilzad and his aides could not be reached for comment early Saturday.
In Washington, an administration official said, "There clearly continues to be disagreement, but talks have not collapsed. They're clearly at a critical stage. I would expect intensive negotiations to continue among everybody tomorrow and through the weekend."
The attack in Mosul targeted members of the Iraq Islamic Party, which had been lobbying for Sunnis to take part in the coming elections. Iraq's Sunni minority largely boycotted the January elections that seated the current transitional government, led by Shiites and Kurds. Threats from insurgents also contributed to the boycott. The resulting small turnout left Sunnis with comparatively little clout in the government and in the constitutional talks.
Zarqawi's forces, sheltering in Sunni areas of central and western Iraq, are challenging the Sunni move into the political process with fierce determination.
On Thursday, gunmen opened fire on a Ramadi meeting of political, tribal and religious leaders discussing the constitution. The local governor, leading western Iraq's heavily Sunni Anbar province, was at the meeting but escaped injury.
On Friday, a Saudi insurgent leader, Abu Muhammad Hajeri, of Zarqawi's group, was found dead in Ramadi with three Iraqi members of the insurgency. Sunni tribal members, speaking on condition of anonymity, said tribesmen had killed them.
The killings were in retaliation for tribal deaths in clashes earlier this month, when Sunni tribesmen took up arms to prevent Zarqawi's group from enforcing an edict ordering the expulsion of local Shiites, the tribal members said.
"Even for those [Sunnis] who want to resist, they are starting to see voting as a form of peaceful, nonviolent resistance," said Maj. Ed R. Sullivan, a U.S. military official in Ramadi. "That's a growing trend. The extremists don't want to see that."
Separately on Friday, gunmen killed a city council member in the northern city of Hawija, police said. An Iraqi policeman died in an overnight raid in Baghdad, news agencies said.
In Baghdad, U.N. workers lowered their blue-and-white flag to half-staff in the Green Zone to mark the second anniversary of the Aug. 19, 2003, bombing of U.N. headquarters in the capital.
Knickmeyer reported from Baghdad. Staff writer Robin Wright in Washington, correspondent Jonathan Finer in Baghdad and special correspondents Naseer Nouri and Khalid Saffar in Baghdad contributed to this report.
