Pentagon officials are stopping short of calling it an act of war, but they said Thursday the United States has protested to Iran about the incident, which happened November 1 over international waters.

Defense Department spokesman George Little says the MQ-1 unmanned aerial vehicle, commonly known as a Predator drone, was on a routine classified mission.

“An unarmed, unmanned MQ 1 US military aircraft conducting routine surveillance over the Arabian Gulf was intercepted by Iranian SU-25 Frogfoot aircraft and was fired upon with guns.  The incident occurred over international waters approximately 16 nautical miles [30 kilometers] off the Iranian coastline.  The MQ 1 was not hit and returned to its base safely,” Little said.

The United States routinely conducts surveillance missions over to Iran to check on nuclear facilities and other sites. 

The Pentagon says this is the first time Iran has fired on one of its drones.  Iran says it shot down an American unmanned aerial vehicle last year over Iranian territory.  U.S. officials say that aircraft landed unintentionally.

Officials say President Barack Obama was notified soon after the latest incident.

Confirmation of the incident comes more than week after it occurred, prompting reporters to ask whether the White House ordered disclosure of it withheld until after last Tuesday’s presidential elections had passed.

Little said the Defense Department does not typically comment on classified missions. He said the reports were leaked.

“Someone apparently disclosed this in an unauthorized manner, and that’s unfortunate,” Little said.

Pentagon officials on Thursday said they have made it clear to Iran that they are prepared to respond to Iranian aggression, but did not say if they had any plans to retaliate for the incident.