US President Barack Obama called on Russian President Vladimir Putin to agree to a diplomatic solution in the escalating conflict in Ukraine. Obama reportedly told Putin that "the costs for Russia will rise" if its aggression continues.

In a separate phone call with Ukrainian President Petro Poroshenko, Obama pledged continuing financial assistance to the Eastern European country.

This most recent "telephone diplomacy" comes a day before another round of talks in Minsk, Belarus. The newest talks will be a follow-up to an agreement reached in Minsk last September. NATO countries, led by Germany, France and the United States, are pressuring Russia to withdraw troops and armaments from separatist-controlled territories in Eastern Ukraine.