NATO and the EU have agreed to tighten cooperation against the "hybrid warfare" that the military alliance says Russia has used against Ukraine.
NATO Secretary-General Jens Stoltenberg made the announcement on May 14 after a two-day meeting of the military alliance in the southern Turkish city of Antalya.
He said NATO and the EU will "ensure that the strategies we are developing are complementary, so that we can work together quickly and effectively in the case of a hybrid threat against any of our members."
Russia annexed Crimea in March 2014 by deploying troops in unmarked uniforms.
The West also accuses Russia of supporting separatist rebels in eastern Ukraine with arms and manpower, a claim that Moscow denies.
Russia is accused of carrying out "hybrid warfare" in the conflict by combining classical military techniques with unconventional guerrilla tactics, as well as non-military means like cyberattacks and propaganda.