A senior NATO official said on Monday it was still unclear whether Russia was prepared to take steps to support the Minsk agreement to ease the conflict in Ukraine, adding that Moscow would face more sanctions and isolation if the deal collapsed.
"It is still not clear despite Russia's words, whether in its actual deeds Russia intends to support the implementation of Minsk," Deputy Secretary General Alexander Vershbow told NATO's parliamentary assembly in Budapest.
"Russia is trying to pretend that it's not a party to the conflict and that Ukraine should deal directly with the separatists," he added.
Meanwhile, two Ukrainian serviceman have been killed and four wounded in separatist attacks in eastern Ukraine in violation of a cease-fire agreement, Ukrainian military spokesman Andriy Lysenko said on Monday.
A day earlier, Lysenko had announced that three Ukrainian serviceman have been killed and 17 wounded in fresh separatist attacks in eastern Ukraine in violation of a cease-fire agreement.
Two of the deaths were a result of a mortar attack near the town of Svitlodarsk, northeast of separatist-controlled Donetsk, Lysenko said.
Ukrainian President Petro Poroshenko said last Wednesday that 83 Ukrainian servicemen have been killed in rebel attacks since the cease-fire came into force in February.
The announcement of new Ukrainian fatalities in the conflict with Russian-backed separatists came as Kiev renewed accusations against Moscow of direct involvement in the fighting following the capture of two Russian servicemen.
The bloody conflict has killed more than 6,100 people in just over a year.