US Defense Secretary says Russia trying to redraw borders by force

U.S. Defense Secretary Jim Mattis on a visit to Ukraine on Thursday said Washington would continue to put pressure on Russia over what he called its aggressive behaviour, but stopped short of promising to provide lethal weapons to Kiev.

Mattis said Russia has not abided by the Minsk ceasefire agreement meant to end separatist violence in eastern Ukraine.

"Despite Russia's denials, we know they are seeking to redraw international borders by force, undermining the sovereign and free nations of Europe," Mattis told reporters, alongside Ukrainian President Petro Poroshenko.