Washington says a Russian military jet engaged in an "unsafe interaction" with a U.S. Navy surveillance plane over the Black Sea on January 29, coming within 1.5 meters and crossing directly in front of the U.S. plane.
In a statement late on January 29, the U.S. State Department called on Russia "to cease these unsafe actions that increase the risk of miscalculation, danger to aircrew on both sides, and midair collisions."
Earlier on January 29, the U.S. Navy said the U.S. EP-3 Aries II surveillance plane ended its mission prematurely after the incident in international airspace over the Black Sea.
"The duration of the intercept lasted two hours and 40 minutes," the Navy statement said, adding that the EP-3 was forced to fly through the Russian plane's jet wash.
The Russian Defense Ministry issued a statement saying that an Su-27 fighter had "intercepted a U.S. EP-3E Aries II electronic warfare and reconnaissance aircraft."
Moscow said that "all security precautions" had been observed during the encounter.
The U.S. Navy statement said Russian planes "must behave within international standards to ensure safety and prevent incidents."
"Unsafe actions increase the risk of miscalculation and midair collisions," it added.
There have been numerous close encounters between Russian and NATO aircraft in recent years over the Black Sea, the Baltic region, Syria, and elsewhere.
Russian and NATO-member aircraft have operated in close proximity in the Black Sea after Russia boosted its military presence in the region following Moscow's 2014 seizure of Ukraine's Crimean Peninsula.
Last November, U.S. officials reported a Russian Su-30 fighter had made an "unsafe" intercept of a U.S. Navy P8-A Poseidon in the region.
In that incident, the Russian aircraft crossed in front of the U.S. plane, forcing the U.S. plane through its jet wash and causing "a 15-degree roll and violent turbulence," U.S. officials said.
In April 2014, two Russian fighters buzzed a U.S. guided-missile destroyer. U.S. European Command at the time expressed "deep concerns about the unsafe and unprofessional Russian flight maneuvers."