The European Union is giving Russia and the Ukraine until Monday to settle their gas dispute, saying it will reassess relations with the two countries if the dispute is not resolved.
The prime ministers of Ukraine and Russia are due to meet in Moscow Saturday to discuss the impasse, which has seen gas supplies cut off to much of Europe.
EU spokesman Johnannes Laitenberger said the Russian-Ukrainian talks are the "last and best chance" to end the dispute. He said that if the talks fail, the EU will have to consider whether it can continue to conduct "business as usual" with the two nations.
Meanwhile, Kyiv is preparing to host an "energy security" summit Friday with several eastern European leaders to discuss the gas dispute.
Meanwhile, Russian Prime Minister Vladimir Putin has arrived in Germany, where he is set to meet with Chancellor Angela Merkel for talks likely to include Europe's frustrations over the gas crisis.
Russia said Thursday it had for a third straight day opened a gas pipeline at the Ukrainian border and asked Kyiv to send a limited amount of gas on to Europe.
But Ukraine's national gas company Naftohaz refused, saying the route demanded by Russia's Gazprom for the Europe-bound gas would force Ukraine to shut off gas supplies to millions of domestic consumers. Moscow insists the route is viable.
Angela Merkel, speaking Thursday in Berlin alongside British Prime Minister Gordon Brown, renewed European calls for the gas crisis to be resolved soon. She said Russia risks further tarnishing its reputation as an energy supplier.
Some information for this report was provided by AP and Reuters.