"We are thoroughly working on the documents to reconsider the unfavorable conditions stipulated in the 2009 contracts between Ukraine’s Naftogaz and Russia’s Gazprom," he said.
Gazprom suspended gas deliveries in Ukraine in 2009 because of contractual disputes. The deal ending the impasse left Ukraine with some of the highest natural gas bills in the region.
Gazprom this month lifted a gas discount for Ukraine, which was brokered in December. The Kremlin said Ukraine owes $1.45 billion in gas debts and could face another suspension in deliveries.
"Russia cannot and should not unilaterally bear the burden of supporting Ukraine’s economy by providing discounts and forgiving debts; and as point of fact, using these subsidies to cover Ukraine’s deficit in its trade with EU member states," Russian President Vladimir Putin said in a letter sent Thursday to European leaders,
Europe gets about a quarter of its gas needs met by Russia, though most of that runs through a Soviet-era gas transit system in Ukraine.