Russia is threatening to further cut Ukraine's natural gas supply unless Kyiv reaches on an agreement on debt payment and future deliveries.
Russia's state-run natural gas monopoly Gazprom says the additional 25 percent cut could take place Tuesday. Gazprom has already reduced gas supplies to Ukraine by more than one-third.
Ukraine is warning it could restrict shipments of gas through its territory to Western Europe if Russia makes more cuts. When Russia reduced supplies to Ukraine in early 2006, the action created shortages throughout the region.
Ukrainian President Viktor Yushchenko telephoned Russian President Vladimir Putin Monday to discuss the gas issue.
Russia last week said that Ukraine had cleared its debts for 2007 but that Gazprom is seeking $600 million for gas already delivered this year. Disagreements over contracts for future gas deliveries are also central to the dispute.
The European Union has urged both sides to find a solution.
Some information for this report was provided by AFP, AP and Reuters.
