Russian aircraft have repeatedly challenged USA planes during the past year with maneuvers deemed unsafe, despite a 1972 agreement that Russia assumed from the Soviet Union created to prevent miscalculations in the skies and seas.
"The crew of the EP-3 reported turbulence following the first interaction, and vibrations from the second", the U.S. statement reads.
The Navy EP-3 was operating out of Souda Bay, Greece, according to Pentagon spokesman Eric Pahon.
The duration of the intercept was about 25 minutes, during which the Su-27 made two passes near the EP-3E aircraft.
A Navy EP-3 surveillance aircraft was operating over worldwide airspace when the Russian Su-27 flew at high speed directly in front of it, "which put our pilots and crew at risk", according to a Naval Forces Europe-Africa statement.
The Russian Ministry of Defense has denied US Navy claims that its Su-27 jet intercepted a US EP-3 Aries spy plane in an unsafe manner. A US spy plane Boeing RC-135U made a reconnaissance flight on the Russian western border on last October 19. "We expect them to behave within worldwide standards set to ensure safety and to prevent incidents".
In January, the Russian jet intercepted a USA aircraft and came within just five feet over the Black Sea.
"Despite the fact that Russian military has the right to operate in global airspace, such interaction was irresponsible", the US Navy press service said in Europe and Africa.
Russia's embassy in the United States issued a statement insisting its fighter had "followed all necessary safety procedures".
The Russian Defense ministry acknowledged the incident, insisting, however, that the Su-27 kept a safe distance from the EP-3.
"The jet's crew reported identifying the USA reconnaissance plane and accompanied it, preventing a violation of Russian airspace and followed all necessary safety procedures", the statement from Russian defense officials said, according to Russian state-backed Sputnik News.
Encounters between Russian and U.S.as well as North Atlantic Treaty Organisation warplanes have increased as Moscow has been seeking to demonstrate its resurgent military might.