Sergei Kupriyanov said in an interview with Echo Moskvy radio that Ukraine had outstanding debt for this year's deliveries, but refused to give a figure.
"It is a large amount, but we are trying to negotiate it," he said.
Earlier in November the parties made considerable progress on a long-term contract for gas deliveries to Ukraine and a deal for gas transit through the country. However, the gas price for Ukraine in 2009 and subsequent years has not yet been agreed.
Kiev hopes that the price will be around $250 per 1,000 cubic meters next year. This year, Ukraine has been paying $179.5 per 1,000 cu m.
Gazprom earlier said Russia will supply at least 55 billion cubic meters of natural gas to Ukraine in 2009.
Russian Prime Minister Vladimir Putin and his Ukrainian counterpart Tymoshenko agreed at the start of October on a memorandum on direct natural gas supplies from Gazprom and Naftogaz without intermediaries.
Gas pricing and supply has been a thorny issue in recent years, triggering bitter rows between the two former Soviet republics.
Kupriyanov expressed hope that this year the sides would be able to avoid 2005-2006 scenarios when conflicts around the pricing for gas deliveries to Ukraine led to the interruption of gas supplies to Europe.
