Iraq's violence took two turns this week that carry the potential to send the crisis - and American involvement in it - in new directions.
The execution of one US hostage in Iraq and the grim prospects for two fellow businessmen - another American and a Briton - held by an extremist Islamic group cast a dark shadow over the foreign presence here.
At the same time, the separate killings of two prominent Sunni clerics in Shiite neighborhoods of Baghdad raised again the possibility of sectarian conflict - that Iraq could eventually slip into civil war.
The beheading of an American hostage, claimed by someone identifying himself as Abu Musab al-Zarqawi in a videotape released Monday, seems likely to provoke retaliatory action by the United States. US officials say Mr. Zarqawi is directing attacks from Fallujah, the center of radical Sunni opposition to the Iraqi interim government.
The US responded with a full assault on Fallujah in April after four US contractors were killed and their bodies were desecrated there. The eventually aborted assault ended with even stronger opposition to the US presence in the restive city and such opposition expanding outside the Sunni Triangle.
Monday's beheading of American civil engineer Eugene Armstrong appeared designed to leave in deliberate, cruel suspense the fate of two other hostages, American Jack Hensley and Briton Kenneth Bigley. The two, along with Mr. Armstrong, were abducted from their Baghdad home last week.
The objective: rivet global attention on the fate of foreigners in Iraq even as Iraq takes the center of the world stage. President Bush focused on Iraq Tuesday in a speech at the United Nations, and Iraqi interim Prime Minister Iyad Allawi is in New York and Washington seeking to bolster US and world support for Iraq's transition.
Yet almost lost to Western eyes in the focus on the beheading and the other foreign hostages was the killing of two Sunni clerics in separate incidents in Baghdad Sunday and Monday. Iraq experts fear those killings could feed the kind of religious strife that some forces - including Zarqawi - have sought to provoke.
"Foreign guerrillas killing Iraqi Salafis [conservative, anti-Western Muslims] to provoke Iraqi-on-Iraqi Sunni-Shiite violence is among the few scenarios that make any sense," says Juan Cole, an Iraq specialist at the University of Michigan.
One of the two sheikhs killed, Hazem al-Zeidi, was prominent in negotiating between the Sunni and Shiite sects of Iraqi Islam. Some analysts, zeroing in on efforts since January by Zarqawi to provoke sectarian conflict, see his hand in the killings. But others close to the two Sunni sheikhs say they suspect their opposition to the American presence in Iraq as the motivation for the killings.
"We cannot as yet accuse specific people for these crimes, but we can suspect specific aims," says Muthana al-Dhari, spokesman for the Association of Muslim Clerics. "Those responsible are attacking our well-known opposition to the American occupation of our country. And they are attacking our success in strengthening that opposition with other sects."
Five members of the association, a conservative Sunni group headquartered in Baghdad and best known for its opposition to US troops in Iraq, have been killed since February.
Clerics from the organization have condemned the kidnapping of foreigners, while the organization is said to have intervened on behalf of foreign hostages - an avocation that could draw the ire of criminal groups or some political factions. But the association says none of the five murdered clerics was ever involved in such negotiations.
After one of the two killings occurred in the Sadr City neighborhood, loyal to Shiite cleric Moqtada al-Sadr, some here speculated the killing may have been sanctioned by Mr. Sadr. But Mr. Dhari says the association and Sadr agree on the importance of ridding Iraq of the occupiers, and that they also share the view that Iraq's current interim government is illegitimate because unelected. "I would also point out the demonstrations in Sadr City condemning the killings," says Dhari. "We know people are trying to make trouble between our two sects, but I believe the two sides recognize that and will be able to stay out of the trap."
Some Iraq experts like Michael O'Hanlon at the Brookings Institution in Washington warn that civil war looms larger as violence escalates - emboldening insurgent groups that believe they have time on their side.
Indeed, one outstanding difference separating the Sadr Shiites and Sunnis is the January elections. Sadr said this week they must take place in January as planned, while Sunnis like Dhari say elections won't be legitimate because the Allawi government is contemplating dropping certain districts from the vote - he estimates as much as one-third of the population - over security concerns.
Michigan's Dr. Cole says Sadr supporters have attacked Sunni mosques and driven Sunnis out of neighborhoods in the past. On the other hand, he points to the Sadr "alliance" over the past five months with the Fallujah resistance as having attenuated sectarian differences. "It would be strange," he adds, "if the Sadrists, still under severe US pressure, should choose this moment to alienate these strange political bedfellows."
Some Iraqis criticize the tendency - which they attribute to the Americans - to see Zarqawi behind every bush.
"Our connections on the ground tell us that Zarqawi is at least disabled if not worse, but still we hear his name in connection with every incident," says Daoud Salman, chairman of the department of religious laws at the College of Religious Studies in Baghdad. "At the same time we do not doubt there are forces that would like to see religious troubles here so that Iraq is weakened further and the Americans have to stay longer."