Ukraine's President Petro Poroshenko says it is "difficult" to maintain the ceasefire because "terrorists are trying all the time to provoke" Kiev's troops.
He told a televised meeting of the government that Ukraine is "regrouping" its forces in the east of the country to defend territory, not to stage a new offensive.
He said the peace roadmap agreed last week between Ukraine and pro-Russian separatists preserves the concept of a sovereign, united Ukraine within its current borders.
Were the Russians -as Barack Obama claims - weighed down by sanctions, or where the Ukrainians looking to cut their losses?
The new president of the European Council could be "very important" for David Cameron.