A Russian jet flew within 5ft (1.5m) of a US reconnaissance plane's wing tip over the Baltic Sea on Monday, US officials say.
The encounter was deemed "unsafe" due to the Russian pilot's "high rate of closure speed and poor control of the aircraft," officials said.
But Russia disputes this, saying the US plane made a "provocative" move.
Meanwhile, a Nato jet flew close to a Russian plane carrying the defence minister, Russian media reports say.
The F-16 fighter jet was chased away by a Russian Su-27 military jet over the Baltic, according to the state-owned Tass news agency, which had a reporter on the plane.