US forces shot down an Iranian drone 60 miles (100km) north-east of Baghdad last month, the US military says.
A military spokesman said the Unmanned Aerial Vehicle (UAV) was in Iraqi airspace for almost an hour and 10 minutes before it was engaged.
The US accused Iran of deliberately sending the spy drone into Iraqi airspace, but a top Iraqi official suggested it had been a mistake.
There was no immediate comment from Iran on the 25 February incident.
The US has long accused Iran of military interference inside Iraq.
"This was not an accident on the part of the Iranians," said US military spokesman Lt Col Mark Ballesteros, who identified the drone as an Iranian-made Ababil 3.
Pilots "were directed to shoot the UAV down after determining there would be no possibility of collateral damage", he added.
Maj Gen Abdul Aziz Mohammed Jassim, head of military operations at the Iraqi defence ministry, told Reuters news agency he believed the plane's entry into Iraq had probably been a genuine error.
"It crossed 10km into Iraq," he said. "It's most likely that its entrance was a mistake."
The Ababil 3 is a reconnaissance drone. Israeli forces reported downing several Hezbollah Ababils during the 2006 Lebanon War.