Iran has launched air strikes against Islamic State (IS) militants in eastern Iraq, the Pentagon has said.
Pentagon spokesman Rear Admiral John Kirby said the US believes it may be the first time Tehran has launched manned aircraft from inside Iran to strike targets in Iraq.
The US had not co-ordinated air strikes or military activities with Iran, he said, adding that America continued to fly missions over Iraq and it was up to the Iraqi government to avoid conflicts in its own airspace.
Iranian military leaders have acknowledged that dozens of their forces have been in Iraq fighting alongside Kurdish troops battling the extremists.
The US has not invited Iran to join the coalition fighting IS and Iran has said it would not join in any case.