Aleksandr Medvedev told a news conference that Gazprom "will deliver the amount needed for Europe to Ukraine's gas transit system."
Gazprom, a Russian state-controlled monopoly, supplies about one-quarter of Western Europe's natural gas. The deliveries go through pipelines that cross Ukraine.
Ukraine has been paying $50 per 1,000 cubic meters in exchange for the transit of Russian gas through its territory to Western Europe. Russia wants to raise the price more than four times, saying the increase is needed to bring the gas price to world levels.