The Ministry of Defence (MoD) has failed to provide an inquest with a recording of a "friendly fire" incident in which a British soldier died.
L/CoH Matty Hull was in a convoy of light armoured vehicles near Basra
Oxfordshire Assistant Deputy Coroner Andrew Walker had criticised the MoD for delays and gave officials until Friday to produce the tape.
But the MoD said authorisation from the United States was needed to hand over the video. The case was adjourned.
Lance Corporal of Horse Matty Hull, 25, from Berkshire, died in March 2003.
The cockpit video was taken as a US aircraft opened fire on British troops.
The coroner has adjourned the court until 16 February in order for the MoD to release the classified video.
The BBC has learned that the video was only given to the coroner this week, but clearance is required for the tape to be shown.
The barrister for the MoD said it had not been possible to get permission from the Americans to lift its classified status.
L/CoH Hull's widow, Susan Hull, told BBC News she was "very disappointed but not particularly surprised" by the decision.
Mr Walker said he was sorry his request had not been met. It was vital all evidence was reviewed fully, fairly and fearlessly, and it was crucial the court saw the video before he took more evidence from witnesses.
MoD lawyer Leigh-Ann Mulcahy, said high-level diplomacy between US and UK governments was needed to release the classified recording.
No evidence claim
In a statement the ministry said: "[The] MoD respects the fact that this classified information belongs to the US, in the same way as the US respects our ownership of sensitive information we provide them with.
"Nonetheless, we are in discussions with our allies in the US about how we can, jointly, move this situation forward.
"Everyone understands the concerns of L/CoH Hull's family, and of the coroner himself in this matter."
The MoD was further criticised by L/CoH Hull's family who had previously been told "categorically" there was no such video evidence.
L/CoH Hull, from the Windsor-based Household Cavalry Regiment, died from multiple injuries inside his blazing Scimitar tank despite efforts by colleagues to save him.
He was travelling in a column of light armoured vehicles near Basra, in southern Iraq, when it was reportedly attacked by a US A-10 "tankbuster" aircraft.
Another widow has adding her voice to criticism of the failure to release the video.
Sam Roberts, whose husband Steve was shot dead in Iraq after handing over his body armour, told Five Live Drive that L/CoH Hull's family were being prevented from getting on with their lives.
"What makes it even worse for the family at the coroner's court at the moment is that they know the information is there but they're not being allowed to see it.
"Until you can actually move on and deal with your grief you want to try and get as much information as possible and unfortunately they're not helping with that."