Sergei Kupriyanov told the Moscow-based Echo Moskvy radio station that the "average price for next year" would be "about $280."
Russia's Gazprom and Ukraine's Naftogaz agreed on Tuesday to reduce Russian national gas deliveries by 35% in 2010, from the previously contracted 52 billion cubic meters to 33.75 bcm.
The reduction is likely to cost Gazprom some $5 billion in lost revenues.
Kupriyanov also expressed hope that there would be no repeat of last year's gas problems with Ukraine.
"We cannot rule this out, but we sincerely hope that nothing will happen," he said.
Russia, which supplies around one quarter of Europe's gas, briefly shut down supplies via Ukraine's pipeline system at the start of the year amid a dispute unpaid bills and new prices.
The conflict was resolved in January, when Russian Prime Minister Vladimir Putin and his Ukrainian counterpart Yulia Tymoshenko reached a deal on imports and transit for 2009.
Ukraine transits around 80% of Russia's Europe-bound gas.
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