The two planes came so close together that the EP-3E was forced to fly through the Russian’s “jet wash”, according to US Naval Forces Europe spokeswoman, Captain Pamela Kunze.
She explained: “This interaction was determined to be unsafe due to the SU-27 closing to within five feet and crossing directly through the EP-3’s flight path, causing the EP-3 to fly through the SU-27’s jet wash.
“Unsafe actions increase the risk of miscalculation and midair collisions.
“The US aircraft was operating in accordance with international law and did not provoke this Russian activity.”
Captain Kunze added that the intercept over the Black Sea lasted over two and a half hours.
The Russian defence ministry justified the actions of the SU-27 by claiming it flew “strictly in accordance with international rules”.
In a statement, it added: “An SU-27 fighter was sent to intercept the target and approached the aircraft at a safe distance and identified it as an ER-3E (Aries II) US reconnaissance aircraft.
“The crew of the fighter jet reported the identification of the American reconnaissance aircraft and accompanied it, preventing it from violating Russian airspace, observing all necessary security measures.
“The entire flight of the Russian SU-27 was strictly in accordance with international rules for the use of airspace and there were no extraordinary events.”
CNN military analyst John Kirby blasted the SU-27’s actions as “inexcusable, provocative and potentially fatal”.
He went on: “While it is difficult to determine the degree to which senior levels in the chain of command are involved in the specific conduct of any particular intercept, one thing is absolutely clear: The Kremlin desires to challenge US military patrols in and above the Black Sea and elsewhere.
“It’s a policy we must presume the Russian defence establishment is acting concertedly and aggressively to pursue. Russian military leaders are known for a lot of things. Independent thinking is not one of them.”
Close intercepts have become more common following Vladimir Putin’s annexation of the Crimea that saw him expand his military might closer to the Black Sea.
Russian, US and NATO forces all operate in the vicinity of the area.
Last year saw a Russian SU-30 fighter make an “unsafe” interception with an American P-8A Poseidon craft that caused the latter to experience a “15-degree roll and violent turbulence”.