By Nick Childs
BBC Pentagon correspondent
The US military is blaming a mistake by a marine air controller for what is seen as the worst incident of so-called friendly fire during the Iraq war.
Nasiriya was the scene of bloody close-quarter fighting
Up to 10 US marines may have been killed by friendly fire during fighting around the city of Nasiriya, according to a newly published Pentagon report.
The incident occurred four days into the war, on 23 March last year.
The unidentified air controller could face disciplinary action, but that has yet to be decided.
The incident occurred during intense fighting around the city of Nasiriya. A US marine air controller on the ground called in air support to attack Iraqi positions - not knowing there were dozens of US marines there as well.
A total of 18 marines died in the fighting.
The Pentagon's report says eight were definitely killed by enemy fire - but it is impossible to tell whether the others died from enemy or friendly fire.
The report cites difficult communications and changes in the US attack plan as factors in what it describes as a tragic event.
But the report clears the pilots of the attacking A10 aircraft of blame.