Russian President Vladimir Putin has said that Russia would fulfill its obligations to European gas clients.
He said he had no plans to halt deliveries to Ukraine although Moscow could make Kiev pay in advance for deliveries.
Mr Putin's remarks appeared aimed at easing concerns in Europe but keeping pressure on Ukraine to pay its $2.2bn (€1.5bn) debt for Russian gas and blaming Kiev for any disruptions in supplies across its territory to European consumers.
"I want to say again: We do not intend and do not plan to shut off the gas for Ukraine," Mr Putin said in televised comments at a meeting of his advisory Security Council.
But he added that his government had proposed demanding payment in advance from Ukraine for future supplies.
"We guarantee fulfillment of all our obligations to our European consumers. The question is not about us. The question is about providing transit across Ukraine," he said, suggesting Ukraine might seek to siphon the gas meant for Europe if Russia reduced supplies meant for Ukrainian consumption.
Mr Putin sent a letter to the leaders of 18 European countries that buy Russian gas yesterday.
He warned that deliveries could be disrupted if state-controlled Gazprom cut supplies to Ukraine and calling for urgent talks to seek a solution.
Mr Putin's spokesman said earlier today that the European nations had not yet responded to the letter.
The letter prompted the US to accuse Russia of using energy as a "tool of coercion" amid the biggest East-West crisis since the Cold War.