WASHINGTON (AP) — An Iranian fighter jet approached a U.S. surveillance drone aircraft over the Persian Gulf but broke off its pursuit after a U.S. escort plane discharged a warning flare, the Pentagon said Thursday.

Pentagon press secretary George Little said the incident occurred Tuesday and that the unarmed MQ-1 Predator surveillance drone as well as two U.S. military escort planes remained over international waters at all times.

Little said the drone was conducting a "routine classified" surveillance mission.

He said the Iranian F-4 plane came as close as 16 miles to the drone before it broke away.

In November an Iranian fighter fired upon, but did not hit, an unarmed Predator over the Gulf. In the aftermath of that incident, the U.S. told the Iranians that it would continue to conduct surveillance flights "consistent with long-standing practice and our commitment to the security of the region," Little said.

"We also communicated that we reserve the right to protect our military assets as well as our forces and will continue to do so going forward," he added.