"The US aircraft was operating in international airspace and at no time crossed into Russian territory," said Laura Seal, a Pentagon spokeswoman.
The incident comes shortly after Russian aircraft repeatedly buzzed the USS Donald Cook this past week, including an incident Tuesday in which a Russian Su-24 flew 30 feet (nine meters) above the ship in a "simulated attack profile," according to the US military's European Command.
"This unsafe and unprofessional air intercept has the potential to cause serious harm and injury to all aircrews involved," Seal said of Thursday's incident.
"More importantly, the unsafe and unprofessional actions of a single pilot have the potential to unnecessarily escalate tensions between countries."
The US aircraft in question was an RC-135.