Even as divisive rhetoric and more bloodshed between Iraq's majority Shiites, who control the new government, and disenfranchised minority Sunnis appeared to magnify the prospect of civil war late last week, condemnations of the violence — and even a bid to mediate a truce — began to emerge.

"They have peered over the edge, and decided that is really where they don't want to go, and now people are pulling back," says a U.S. diplomat in Baghdad. He notes "a lot of communication" between Sunni and Shiite leaders to "see how we put this genie back in the bottle."

With 10 clerics killed in the past two weeks, and Sunni mosques closed in protest for three days over the weekend, tensions have escalated. But even Moqtada al-Sadr, the firebrand Shiite cleric whose militia took on American forces during two uprisings last year, began a mediation effort Sunday.

To ease tensions, Mr. Sadr's envoys began talks Sunday with representatives of both main Shiite and Sunni parties — the Supreme Council of the Revolution in Iraq (SCIRI) and the Muslim Clerics' Association, respectively.

Hard-line Sunni militants are largely behind Iraq's insurgency, which has killed some 500 Iraqis in recent weeks with suicide car bombs. For many months, Shiites have been heavily targeted in an apparent bid to provoke a sectarian backlash and draw them into open conflict.

The latest wave, however, includes the killing of a prominent Sunni leader and member of the Muslim Clerics Association, who was whisked away with other Sunnis by men in Iraqi uniforms.

The Clerics Association is alleged to have links to the insurgency, but has also helped secure the release of Western hostages. Its leader, Harith al-Dhari, accused Shiite militiamen of the Badr Brigade, the Iran-trained military arm of one of Iraq's most influential political parties, of being "behind the campaign of killings of preachers and worshippers."

A senior Badr official denied the claim, saying it would "only serve to pour fuel on the flames."

Grand Ayatollah Ali al-Sistani, the most revered Shiite leader in Iraq, has long called for restraint to limit revenge. But one of Mr. Sistani's representatives in Baghdad was himself gunned down late last week.

"[Sistani] has placed enormous restraint on his followers — [and] that one fact prevents Iraq falling into a bloodbath," says Imam Hassan Qazwini, a Shiite religious leader from Iraq, who heads the Islamic Center of America in Detroit, Mich.

The Clerics' Association is "still in the shadow of Saddam Hussein; they still do not accept the reality that Sunni domination is gone," says Mr. Qazwini. "If there is a civil war, the Sunnis will pay the price. They know that, and should be the ones who are worried."

The Sunni decision to boycott January elections means that Sunnis hold only 17 spots in the 275-seat National Assembly, which has begun work on a new constitution. Some 1,000 Sunni clerics and tribal leaders met in Baghdad on Saturday, calling for Iraqi unity and vowing to rejoin the political process.

In a statement, the new coalition agreed that "resisting the occupier is a legitimate right," but condemned "all terrorist acts that target civilians, no matter the reason."

Some analysts say that the scale of violence and the rhetoric of Abu Musab al-Zarqawi, the self-proclaimed leader of the insurgency, should not blur the line between acts of terror and those of Sunni resistance. In a statement widely rejected by Islamic scholars last week, Mr. Zarqawi justified the killing of innocent Muslims civilians for jihad.

"There is a difference: the Shiite clergy have not been killed by the [Clerics' Association], but by Zarqawi, who is not under their control," says Mustafa Alani, head of the security and terrorism studies program at the Gulf Research Center in Dubai. The association has "no militia, and all people know their influence over Zarqawi is limited, if anything."

Mr. Dhari's charge that the Iran-trained militia of Mr. Hakkim's SCIRI has infiltrated the interior ministry and security services is a "major accusation," says Mr. Alani. "This is a problem if people in [national] uniform are serving their party with assassinations and killings."

The U.S. diplomat said that so far he has seen "no evidence" of such a link. But he acknowledges that the appointment as interior minister of Bayan Baqir Jabor, a top SCIRI leader, is a "real lightning rod" that has been "very sobering to the Sunni community."

The Sunnis meeting on Saturday called for Mr. Jabor's resignation. Jabor has denied the charges, saying his ministry "didn't kill anybody," and that it would cooperate with any group to dent the insurgency.

The stakes are high, as Shiites and Sunnis weigh their complaints. "I don't believe civil war is possible at this stage," says Ansari. "But if organized [attacks] continue, Sunnis will be forced to form a militia" that could ally with Zarqawi. "Though they do not have the same aims or the same ideology, they would be fighting the same enemy," he adds. "The pressure from the other side will force [Sunnis] to form this for their own self-defense."

Sectarian civil war is a leap for most Iraqis, who have had a message of nationalism drilled into them for a generation, during Saddam Hussein's rule, say observers.

"That nationalist message was very successful, and up to [late 2004] it was rude to ask a person in Iraq what sectarian group they were," says Toby Dodge, an Iraq expert at the International Institute of Strategic Studies, a think tank in London.

What changed, says Mr. Dodge, is that U.S.-installed interim governments — inspired by Iraqi exiles with a "highly divisive sense of Iraqi society" — were created to achieve sectarian balance. The Shiite alliance of parties that won most seats in the election waged a very sectarian campaign that Dodge calls "ethnic entrepreneurialism."

"Most depressing is that when you don't have a state, and you have a law-and-order vacuum," adds Dodge, "Iraqis must depend on local, communal support — built on sectarian appeal."