Russia and Ukraine today signed a deal for the resumption of Russian gas supplies to Europe, where hundreds of thousands of homes have been without power for a week in the depths of winter.

The transit deal, also signed by the European Union, should ensure that Russia resumes sending gas by 0800 GMT tomorrow, and supplies start to flow across European borders about 36 hours later, on Wednesday night.

“The document has been finally signed,” Alexander Medvedev, deputy chief executive of Gazprom, Russia’s state gas export monopoly, told a news conference in Brussels.

The EU’s energy commissioner, Andris Piebalgs, told reporters: “Russia has announced all conditions have been met and we expect now that gas will be flowing in the morning.”

Gazprom and Ukraine have said it will take at least 36 hours before gas reaches EU borders after flows resume.

Russia cut off domestic supplies to Ukraine on New Year's Day in a row over gas pricing. The row escalated as Moscow accused Kiev of siphoning off supplies transiting through Ukraine bound for Europe, and most supplies halted a week ago. Only countries with large gas reserves were unaffected.

An initial deal between the two sides was reached at the weekend, brokered by the Czech Republic which holds the rotating EU presidency, but Russia announced last night that extra conditions imposed by Ukraine had invalidated it.

Gazprom said today that the Ukrainians had backed off from their extra demands. and signed a deal this morning to allow independent monitors to track natural gas supplies from Russia to Europe.

The row came at a bad time for Bulgaria and Slovakia, both heavily dependent on Russian gas and experiencing the coldest winter snap in years.

Austria, the Czech Republic, Germany and Italy came to the aid of the worst-hit eastern European countries, but Slovakia, which is almost entirely reliant on Russian gas, announced its intention to relaunch a Soviet-era nuclear reactor to avoid a possible power blackout.

The Jaslovske Bohunice reactor was shut down on December 31 in line with Slovakia's terms of accession to the EU in 2004 because it failed EU safety standards, but Bratislava says that a treaty provision allows for it to be cranked back up in an emergency - although in Brussels the European Commission said that there was “no legal base” for the relaunch.

Mirek Topolanek, the Czech Prime Minister, whose country has been helping out its neighbour during the crisis, was more understanding. “At the moment, I take it rather as a demonstration of their readiness to tackle an issue that the European Union cannot resolve for Slovakia - a looming blackout,” he said.

Slovakia's decision will be discussed by EU energy ministers, who are attending an emergency meeting today to discuss the crisis and ways to achieve long-term energy security, such as alternative energy sources, building gas pipelines and improving cooperation. Russia provides 25 per cent of the EU's gas needs.

“The crisis must encourage member states to make energy security a bigger priority than it has been so far,” said Martin Riman, the Czech Industry and Trade Minister.

He said the EU must accelerate talks on to avoid being caught up in such supply disruptions. “This crisis should be an encouragement, a kick for us all to start working faster and seriously on the projects.”

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