A Russian fighter jet fired flares directly at a US drone on a mission against ISIS over Syria in what Washington said was the latest episode of “unprofessional behaviour”.
The incident on Sunday severely damaged the MQ-9 drone's propeller, the US Air Forces Central Command said.
The crew operating the drone was able to maintain flight and return it to its home base, the US said.
“The Russian fighter’s blatant disregard for flight safety detracts from our mission to ensure the enduring defeat of ISIS,” said Lt Gen Alex Grynkewich.
“We call upon the Russian forces in Syria to put an immediate end to this reckless, unprovoked and unprofessional behaviour.”
State Department spokesman Vedant Patel said he would not speak of any action the US might take after the incident.
"What I will just reiterate, though, is that we've been clear that Russia needs to stop these reckless and threatening types of behaviour that could result in the loss of life and put people in harm's way," Mr Patel said.
Russian aircraft have been harassing US aircraft over Syria, the US military said.
Last week a US MC-12 on an anti-terrorism mission was “closely approached” by a Russian Su-35 jet. The US aircraft was forced to fly through the Russian fighter's turbulence.
“Russian unsafe and unprofessional behaviour in the air not only degrades our defeat-ISIS mission, it risks unintended escalation and miscalculation,” said Gen Michael Kurilla, head of the US Central Command.
Joint chiefs of staff chairman Gen Mark Milley said there was nothing to suggest the sharp rise of aggressive incidents over Syria is related to the war in Ukraine.
Gen Milley said the US military has a deconfliction channel to prevent escalation.
