Two Russian-made SU-25 fighter jets opened fire in two separate bursts on the U.S. Predator drone roughly 16 miles off the Iranian coast just before 5 a.m. on Nov. 1, Pentagon spokesman George Little told reporters on Friday.
It is unclear if the fighters intentionally avoided hitting the drone, or if they missed.
The U.S. has previously flown drones over Iran, such as the RQ-170 that Iran claims to have hijacked to land last year. The Pentagon claims that drone malfunctioned.
Little says the drone Iran attacked in November was conducting "routine" but classified maritime surveillance 16 miles off the coast.
That proximity still might have provoked the Iranians into engaging, particularly from the Revolutionary Guard Corps, known for acting more brashly than other military units, says Lamrani.
Dempsey's choice of words could indicate that the U.S. does not plan to retaliate, says Michael O'Hanlon, senior fellow for the 21st Century Defense Intiative at the Brookings Institution.
The U.S. military used similar language to condemn North Korea for reportedly sinking the South Korean ship "Cheonan" in 2010, he says.
"That too was 'hostile' and even more, by analogy, yet we didn't retaliate," says O'Hanlon. "This is in that category. But the Iranians are on notice that we consider this quite unfriendly."
"I don't think it moves the needle too much beyond that," he says of a potential escalation between the U.S. and Iran.
But Lamrani believes the two countries are approaching a "red line" with this most recent attack on the unmanned drone.
"Any further escalation beyond this is basically shooting at manned aircraft," he says. "Anything like that would definitely elicit a response. It's a dangerous game, it's a dangerous situation with how far [Iran] is willing to take it."
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Paul D. Shinkman is a national security reporter for U.S. News & World Report. You can follow him on Twitter or reach him at firstname.lastname@example.org