A US drone's propeller was severely damaged when a Russian jet dumped flares on it while flying "dangerously" close overhead in Syria, says the US.
The US military accused Russian jets of "blatant disregard for flight safety".
The 23 July incident is the latest in a series of "buzzing" encounters between Russian, US and Chinese aircraft.
While Russia has not commented on the latest incident, earlier this week it accused US and allied jets and drones of "violating Syria's airspace".
Moscow also accused the US and allies of violating "deconfliction" protocols that were set up in 2019 to avoid confrontations in Syria's skies.
The BBC has contacted the Russian embassy in Washington DC for comment.
In a statement published on Tuesday, the US military said the Russian fighter plane had harassed the drone while it was on a mission against the Islamic State on Sunday.
US Central Command - which oversees operations in the Middle East - said the jet "deployed flares from a position directly overhead, with only a few metres of separation between aircraft".
Despite being damaged, the MQ-9 Reaper drone was able to be remotely directed back to its home base, according to the US.
Lt Gen Alex Grynkewich, of Central Command, said: "We call upon the Russians in Syria to put an immediate end to this reckless, unprovoked and unprofessional behaviour."
US forces still regularly conduct air-and-ground missions alongside allied forces in Syria and Iraq.
In June alone, US forces carried out 37 sorties that resulted in 13 Islamic State operatives killed and 21 detained, according to the American military.
These missions, US commanders say, have increasingly been harassed by Russian aircraft.
On 7 July, for example, the American military says Russian forces buzzed another US drone for two hours shortly before the unmanned aircraft killed an IS leader in eastern Syria.
Less than two weeks later, on 16 July, a Russian jet flew close to a manned US surveillance aircraft, forcing it to fly through its wake turbulence, and endangering the four crewmembers, said the US.
Similar incidents - including at least one collision between a Russian drone and US jet - have been reported in the Black Sea and the Baltic.
But Case Western University Professor Michael Scharf, a former state department legal adviser, told the BBC "the US is on shaky legal ground in Syria".
"Russia has been invited in by the Assad regime," he said. "The irony here is that Russia has a better legal claim."
Prof Scharf said that while such incidents "used to be seen as a really scary precursor to war", these encounters were unlikely to escalate.
"There's no overreacting and Russia has bigger fish to fry in Ukraine," he said.
Other "buzzing" encounters have also been reported between US, Canadian and Chinese aircraft operating in the Pacific.
