"Action from America, which has the power to force Russia into peace," he continued. "Action from Europe, which has no alternative but to be strong. Action from others around the world who called for diplomacy and an end to the war -- and whom Russia has ignored. There must be strong pressure for the sake of peace."

Technological advances have given threadbare militaries and rebel fighters the ability to strike stunning blows against far stronger forces.

Russia claimed Sunday that its forces are for the first time pushing into the central Ukrainian region of Dnipropetrovsk, an area it has been trying to reach for months, in a move that could create new problems for Kyiv’s much-stretched forces.

Russian officials say that Moscow is still awaiting confirmation from Kyiv on a planned exchange of 6,000 bodies of soldiers killed in action and is accusing Ukraine of delaying the process