Russia has conducted large-scale unannounced military exercises "with increasing frequency," straining its relationship with NATO, the alliance's No. 2 official has said.
Speaking on a visit to Bucharest on August 29, NATO Deputy Secretary-General Alexander Vershbow said there had been about a dozen such drills in the past two years.
NATO members haven't staged snap exercises since the end of the Cold War, Vershbow added.
He also said the alliance wants to "develop a more stringent regime to increase transparency and ...predictability and a way to better stabilize what is a very unsatisfactory relationship with Russia."
"If there is an interest in Moscow in stability and predictability, then these exercises are not the way to go," Vershbow added.
The comments come after Russia launched on August 25 large-scale snap military exercises on land and in the Black and Caspian seas, increasing worries in Ukraine and other Western neighbors about Moscow's intentions.