"As soon as we start pumping the gas at the entry point, it should appear at the exit point," Gazprom spokesman Sergei Kupriyanov said in a statement.
Kupriyanov explained that there was still gas in the pipelines even though supply has been completely cut off since last Wednesday and that this should ensure that gas supplies flow more quickly.
"Comments by Ukraine that 36 hours are needed from the arrival of transit gas from Russia into Ukraine's gas network until it reaches Ukraine's western border evoke disbelief and do not meet the current contract," he said.
"From the start of supplies of Russian gas at the entry point into Ukraine's gas transport system, the volume of gas exiting from the western border of Ukraine must correspond exactly to the quantity supplied," he added.
Russia has accused Ukraine of illegally siphoning off gas after it cut off supplies to Ukraine's domestic market on New Year's Day. Ukraine has vehemently denied this charge and accuses Russia of deliberately provoking a crisis.