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.
US President Barack Obama has said it was clear Russia "violated just about every commitment they made" in the Minsk agreement over the situation in eastern Ukraine.
"But Russian aggression has only reinforced the unity of the United States, Germany and our allies and partners around the world", Obama added.
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.