The United Nations Security Council will meet for an emergency session to discuss the crisis in eastern Ukraine today.
A diplomatic source has told Reuters the council will meet at 1am UK time at Russia's request.
Another diplomat has said negotiations are underway on Ukraine's participation.
Tensions remain high in eastern Ukraine after at least three died in a day of shooting during what was supposed to be an Easter truce.
In an exclusive interview with NBC News, the Ukrainian Prime Minister warns of the dangers of unchecked Russian expansion and aggression.
Russia, the US and the EU say that all sides have agreed to steps to "de-escalate" the crisis in Ukraine at talks in Geneva.