Iran's military launched a drone to warn off a reconnaissance plane trying to approach Iranian war games on the Gulf coast, the semi-official Fars news agency said on Saturday.
The report did not specify the nationality of the reconnaissance aircraft, but Iranian forces have had repeated similar confrontations with US forces in the Gulf.
There was no immediate US reaction available.
Iran launched annual joint naval, air, and ground exercises in the Gulf on Friday near the strategic Strait of Hormuz waterway.
"During the exercises, a P-8 manned intelligence aircraft belonging to extra-regional forces, which had tried to reduce altitude to collect more accurate information from the exercise area, was forced to leave the area by the firing of a Karrar drone by (Iran's) air defense," Fars said.
The US Departments of Defense and State did not immediately respond to requests for comment.