The US Pentagon has been given details of fresh allegations made to the BBC about the conduct of US troops in Iraq.
The Marine Corps is under fire over the Haditha allegations
The so far unsubstantiated allegations, were made by US deserter Chris Mogaoay, who fled to Canada as he was training for deployment to Iraq.
He said he and comrades were told that if they shot a civilian they should throw an assault rifle down by the body and claim the victim was an insurgent.
The Pentagon has not yet responded to the allegations.
Mr Mogaoay said he and his comrades were told the rest of the platoon would back the story.
His sergeant showed them pictures, he said, of "what war was really like".
"The first picture he showed me was him lighting a cigarette off of a burning Iraqi's body," he said.
"This disgusted me because this was a man I respected as a marine, someone I'd like to follow into battle."
Mr Mogaoay is one of hundreds of American soldiers who have fled to Canada, rather than serve in Iraq.
He was from the Marine Corps, the same branch of the military said to be involved in the alleged massacre of 24 Iraqi men, women and children at Haditha.
The US military is currently investigating several cases of alleged misconduct in Iraq, including the killing of civilians in Haditha last November.
But Pentagon officials in Washington say a US military investigation is satisfied that US troops used appropriate force in another incident in Ishaqi north of Baghdad in March.
There had been allegations by Iraqi police that US troops had shot dead 11 civilians, including women and children, in a raid on a house.