US General David Petraeus has spoken directly to the father of British aid worker Linda Norgrove to express his regret at her death.
The commander of international forces in Afghanistan admitted he was "disturbed" it had not been made clear immediately that an American grenade could have killed Ms Norgrove during a rescue attempt.
The comments came as Gen Petraeus fielded questions at an event organised by the Royal United Services Institute (Rusi) in London.
Asked if he could provide any "greater clarity" on the situation, he replied: "This morning I talked with Mr Norgrove and conveyed to him not only the most sincere condolences but also an update on the investigation that is ongoing.
"This is an active investigation and I don't want to speculate.
"It was disturbing clearly not to have the correct facts that morning after the operation was conducted, and to be provided with those later after the taskforce commander conducted further examination, including watching about six different videos of the operation."