Western leaders have accused Russia of "destabilizing" eastern Ukraine.
Meeting at the NATO Summit in Wales, they said they plan to increase pressure on Russia unless it backs down.
NATO's Secretary-General, Anders Fogh Rasmussen, accused Moscow of "attacking Ukraine".
Our correspondent Olly Barratt, who is covering the summit in the Welsh city of Newport.
IN: "Russia coming in…."
OUT: "….Russian aggression"
DUR: 42 seconds
http://www.fsnradionews.com/feeds/0904nato-barratt1.mp3
(ALT)
Correspondent Olly Barratt, covering the summit in the Welsh city of Newport, says while Ukraine has dominated the first day of the meeting, the leaders are also expected to focus on the battle against Islamic State militants in Iraq and Syria.
IN: "It's unlikely…."
OUT: "….a British hostage"
DUR: 42 seconds