WALES - Western leaders have criticised Russia for its "destabilising" influence on the crisis in Ukraine, at the start of a Nato summit in Wales.
Nato and the UK warned that pressure on Russia would be increased if it did not change course in eastern Ukraine.
Prior to the summit, Ukraine's president briefed US and EU leaders on earlier discussions on a ceasefire plan with Russian President Vladimir Putin.
Some 2,600 people have died in fighting between Ukrainian troops and rebels.
The West says it has evidence that Mr Putin is supporting the separatists with training and arms, and has sent Russian troops across the border. Russia denies the accusation.
The conflict has forced more than a million people from their homes in eastern Ukraine, according to United Nations estimates.
Ukrainian government forces have recently suffered several losses, after rebels launched offensives in both the Luhansk and Donetsk regions, and further south around the city of Mariupol on the Azov Sea.
Reports are emerging that the separatists have begun shelling the outer defences of Mariupol.
At least two military vehicles were seen on fire in the area, and eyewitnesses spoke of gunfire.