The US State Department has rejected a coroner's conclusion that the "friendly fire" death of a British soldier in Iraq was unlawful and a criminal act.
Lance Corporal of Horse Matty Hull, 25, died near Basra on 28 March 2003 when a US pilot fired on his tank convoy.
US spokesman Sean McCormack said it was a "tragedy" during a time of war.
The coroner was critical of US failure to send witnesses to the inquest but the Pentagon said he had access to most information from its own inquiry.
Speaking at a State Department briefing in Washington, Mr McCormack said: "Clearly we don't agree with the assessment. What we have here is a tragedy that occurred during a time of war.
"We have conducted an investigation into the matter - our military has - they have come to their own conclusions.
"We certainly would not agree with any conclusion that categorised this as a criminal act."
Recording a narrative verdict, Oxford assistant deputy coroner Andrew Walker said L/Cpl Hull's death was "entirely avoidable".
"It was unlawful because there was no lawful reason for it and in that respect it was criminal," he said.
The US pilots from the Idaho Air National Guard should have flown lower to confirm identities before opening fire, he added.
"I don't think this was a case of honest mistake."
Speaking after the verdict, L/Cpl Hull's widow Susan said she was now prepared to "draw the line" on the event.
"I think all of our family feel it was the right verdict. It was what we'd waited four years to hear," she said.
"It's been a long and painful time and we need to move forward."
But she said the lack of co-operation from the US was "very disappointing".
The Ministry of Defence said it was "very sorry for confusion and upset" caused by the delay in releasing video footage taken from the cockpit of the US A-10 plan.
The recording was not initially shown to the inquest, but the US authorities only agreed for it to be released after the footage was leaked to the Sun newspaper.
An MoD spokesman said a team has been set up to liaise with coroners and bereaved families and to ensure documents are made available quickly to future inquests.
Lawyer Geraldine McCool said the verdict did not suggest there would be a prosecution of the US pilot and the Hull family would not be calling for one.
Constitutional affairs minister Harriet Harman, who met with US diplomats in London ahead of the inquest, said she shared the "frustration" at their failure to send witnesses.
"I explained that this was not a criminal court, nobody could be found guilty and sent to prison, it is simply asking questions and requiring answers," she said.
In a statement the US defence department described the incident as a "tragic accident".
The Hull family believes key information was blacked out of a US Friendly Fire Investigation Board Report given to the coroner investigating his death.
But the Pentagon said the US shared all the information from its inquiry with the MoD, except those parts that had to be withheld for "security, privacy or other reasons".
"The investigation determined that the incident took place in a complex combat environment, the pilots followed applicable procedures," it said.