The killing of two Sunni clerics earlier this week could be part of a slide toward sectarian civil war, analysts say.
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.