EU Commission President Jose Manuel Barroso has said the EU can no longer accept excuses for the failure of Russia and Ukraine to restore gas supplies.
A gas payments row between Moscow and Kyiv has affected most EU nations amid freezing temperatures.
EU officials are meeting Ukrainian and Russian officials in Brussels in an attempt to get the gas flowing again.
A spokesman for the Czech EU presidency said Russia had promised to restore the flow of natural gas through Ukraine at 8am tomorrow.
However, Gazprom replied that it hoped to get the gas restored, but this would only happen once pipeline monitors were in place in Ukraine.
The Ukrainian government earlier signed a new version of a deal designed to reopen Russian gas supplies.
Kyiv had been accused of trying to change an earlier version.
Ukraine had added articles to the accord denying it owed Russia money for gas or that it had stolen gas, according to a version seen by news sources.
Russia's major gas company, Gazprom, had talks in Kyiv this morning. Following that the Ukrainian side signed the 'Rules on Monitoring Gas Transit' with no additional provisos.
Watch a news conference at 4.25pm.
Russian President Dmitry Medvedev had said supplies would only resume once Ukraine signed the document and teams of monitors were in place.
The EU's Czech presidency said this morning that Russia had no further reason to withhold gas supplies.
An EU-brokered accord on terms for a resumption of the supply collapsed over the weekend when Russia accused Ukraine of secretly altering the deal.
