US and Russian aircraft often have encounters in the region, some of which the United States has slammed as unsafe and/or unprofessional.
The Navy aircraft had its transponder on and was conducting "routine operations in global airspace".
The Russian military has not officially commented on the situation but state media coverage has been overwhelmingly skeptical about claims Moscow's aircraft was at fault.
"The Russian fighter approached the air target and identified it as a USA reconnaissance plane P-8A Poseidon".
"The P-8 was forced to fly through the jet wash of the SU-30", Baldanza said.
"Americans have nothing to do in the Black Sea".
Citing the press office of the Southern Military District, Russia's official news agency TASS said the military detected an aircraft at 1.00 p.m. Moscow time (1000GMT) Saturday approaching the Russian border at "high speed".