US officials say they formally complain about Russia's interception of a US reconnaissance plane.
The incident occurred over the Baltic Sea on 7 April, according to the United States European Command, which called the interception "unsafe" and "unprofessional".
US officials say the plane was in international airspace at the time.
The Russian defence ministry denied any wrongdoing on the part of its pilots, according to Russian media reports.
Russian Maj Gen Igor Konashenkov said the US plane had been "steadily moving towards the Russian state border," according to Interfax news agency.
A Russian jet "was scrambled, which approached the unidentified aircraft [and] flew by it several times," after which it changed course, Maj Gen Konashenkov said.
US officials say the fighter intercepted the US aircraft at a high rate of speed from the rear, and then proceeded to conduct two more passes using "unsafe and unprofessional manoeuvres" in close proximity.
Russia has been accused of border violations several times by its Baltic neighbours in recent months.
Baltic states have expressed concern at increasingly frequent snap Russian military drills in the region amid tension over the crisis in Ukraine.