MOSCOW, Feb. 3 – Ukraine’s national energy company Naftogaz Ukrayiny on Monday said non-payments by its clients mean it may fail to pay Gazprom on time for natural gas imports, a bill which the Russian monopoly says has reached $3.3 billion, Reuters reported.

Moscow and Kiev have a history of troubled gas relations, often with regional implications, as most of Russia's exports to Europe are pumped through Soviet-built pipelines that traverse Ukraine.