The White House is condemning the beheading of an American contractor in Iraq whose murder has been posted on an Islamic Web site.

White House spokesman Scott McClellan said that the president's thoughts and prayers are with the family of Nick Berg, a 26-year-old contractor who went to Iraq seeking contracts to repair antennae.

A videotape posted on an Islamic Web site shows five masked men standing behind Mr. Berg. One of the captors reads a statement saying the beheading is retaliation for the abuse of Iraqi prisoners in U.S. custody. They then pushed him to the floor, someone screams and his severed head is displayed for the camera.

Mr. Berg's body was found near Baghdad on Saturday.

Mr. McClellan said that the murder reflects the true nature of those opposed to freedom and democracy in the region. He added that those responsible have no regard for the lives of innocent men, women and children and that they will be pursued and brought to justice.

On the videotape, those responsible for the beheading claim to be part of the al-Qaida terrorist group. That claim has not been authenticated.