There has been widespread revulsion in the United States at the beheading of a US civilian held captive by Iraqi militants.
A videotape of the killing of 26-year-old Nick Berg, who went missing in mid April, was posted on an Arabic language website.
The video showed five hooded men standing behind Mr Berg while one of them read a statement denouncing the abuses of Iraqi detainees by US soldiers at Abu Ghraib prison.
Reports say the businessman from Pennsylvania was then hacked to death with a knife.
The victim's body was was found on Saturday near Baghdad.
Mr Berg's parents have said their son might be alive if he had not been held for nearly two weeks by Iraqi police in late March.
His father, Michael Berg, said they were angry at the lack of information from the US government about his detention, which caused his son to miss a flight home.
Members of the United States Congress set aside several hours today to view a video and other images of abuse of Iraqi prisoners by their American guards.
