A Russian fighter jet made several passes at low altitude near a US destroyer cruising in international waters in the Black Sea at the weekend, the Pentagon says, branding it "provocative and unprofessional".
The incident comes amid the most serious rupture in relations between Moscow and the West since the Cold War over Russia's actions in Ukraine.
Colonel Steven Warren, a Pentagon spokesman, said: "On April 12, a Russian Su-24 made numerous close-range, low-altitude passes in the vicinity of the USS Donald Cook, while the Cook was conducting operations in international waters in the western Black Sea.
"The aircraft did not respond to multiple queries and warnings from Donald Cook. The event ended without incident after approximately 90 minutes."
He added: "This provocative and unprofessional Russian action is inconsistent with international protocols and previous agreements on a professional interaction between our militaries."
The plane "appeared to be unarmed", Warren said.
