The White House said President Barack Obama urged Russian President Vladimir Putin in a phone call to agree to a peace deal.
"If Russia continues its aggressive actions in Ukraine, including by sending troops, weapons, and financing to support the separatists, the costs for Russia will rise," the White House statement added.
A Russian diplomatic source has said a peace deal on Ukraine is 70 per cent likely to be reached at talks today being held in Minsk, reports Reuters.
The source added that Russian President Vladimir Putin and Ukraine's leader Petro Poroshenko were not "travelling to Minsk for no reason".
Video footage recorded from Kramatorsk, deep inside Ukrainian-government controlled territory, shows rockets landing on civilian areas.
Video footage appears to show the moment a shell strikes a community soup kitchen in eastern Ukraine.
A mother in eastern Ukraine buries her son - yet another casualty in a civil war that is killing civilians with appalling randomness.