AFP reports the United States said Wednesday that Russia and separatist rebels were still not complying with a ceasefire in Ukraine, despite a lull in the killing. "To date, neither Russia nor the forces it is supporting have come close to complying with their commitments," Secretary of State John Kerry told US lawmakers, renewing warnings that Moscow would face further sanctions. A day earlier, Kerry had said the Russians were persisting in "lies... to my face" about their activities in Ukraine. The US dismisses Moscow's denials about giving military backing to the separatists in east Ukraine. Russia has in turn warned it could cut off gas supplies to Ukraine within days -- and, by extension, to parts of the European Union.