Russia's natural gas monopoly Gazprom has warned Ukraine against siphoning off gas intended for Europe.
Gazprom Deputy Chairman Alexander Medvedev said Sunday that Ukrainian officials had made threats to tap natural gas from a pipeline running through Ukrainian territory, if supplies intended for Ukraine are cut off.
The two sides have failed to resolve a dispute over Moscow's demand that Ukraine pay more than quadruple the current price for gas imports from Russia.
Gazprom threatened to halt gas deliveries to Ukraine on January first unless Kiev agrees to its new pricing structure. Gazprom held an exercise Friday simulating such a stoppage. Ukraine says such a sharp increase would harm its economy.
Both sides say they may turn to an international arbitration court for help.
Some information for this report provided by AP and Reuters.