US Secretary of State John Kerry said he warned Russia that it would face further sanctions if the conditions of the truce agreed in Ukraine last month were not met.
Speaking at the opening session of the Human Rights Council, Mr Kerry said the pro-Russian forces had a "piece-meal" approach to the ceasefire agreement, accusing them of only withdrawing heavy weapons from the front line in some areas.
Russian Foreign Minister Sergey Lavrov in his address to the Council, said there had been "tangible process" with the ceasefire.
Mr Kerry said he warned Mr Lavrov during their meeting on the sidelines of the session that Russia will face further sanctions if the conditions were not met in full, but also expressed hope that the truce could be completed soon.
"I'm very hopeful that it will in fact be the start of a change which would be an improvement for everybody," he told a news conference in Geneva.