The semiofficial FARS agency on Friday carries quotes from a general in the Iranian Revolutionary Guards as saying that following the Pentagon claim, Iran would confront any "flying object" that entered its air space.
Gen. Masoud Jazayeri said Iranian forces would respond strongly to any ground, sea or air "invasion."
On Thursday the Pentagon said an Iranian military plane fired on, but did not hit, an unarmed U.S. drone aircraft a week ago. A Pentagon spokesman said the drone was in international airspace over the Persian Gulf.
Tensions between the U.S. and Iran have been high over Iran's suspect nuclear program.