MOSCOW (AFP) - Russia and Ukraine on Sunday announced a new deal which they said would allow natural gas to start flowing again, but the European Union remained doubtful about an end to the crisis. Millions in Europe have been left shivering through winter without heating after gas supplies were turned off and while the new accord was to be signed on Monday, the European Union said it had no idea when heating could be turned on again. "We welcome the announcement of a political accord, but we are quite cautious because there have been too many broken accords and promises not kept," a spokesman for the Czech presidency of the EU said in a statement. Russian Prime Minister Vladimir Putin announced the new deal after marathon, late-night negotiations with his Ukrainian counterpart Yulia Tymoshenko in Moscow. "Shortly the gas transit " as the Ukrainian side assures us " will be resumed," he said, speaking alongside Tymoshenko. Tymoshenko said the Russian and Ukrainian state gas firms had been told to draw up agreements on the price of gas and how it will be shipped to Ukraine and Europe by Monday. A spokeswoman for the Ukrainian prime minister said she would return to Moscow for the signing ceremony. The crisis erupted on Jan 1 when Russia cut gas to Ukraine's domestic market over unpaid debts and demands for a higher price in 09. The dispute escalated when Moscow halted all supplies for Europe transiting through Ukraine, accusing Kiev of stealing gas. Heating has been cut for millions in eastern and central Europe and factories and schools closed. Thousands staged a demonstration in the Bulgarian capital on Sunday calling for the reopening of an old nuclear power plant. A previous deal collapsed last week when Russia accused Ukraine of adding hand written articles to the accord. The European Union presidency said the real test this time would be whether Russian gas quickly reached European consumers. "We welcome the progress achieved in the talks between the representatives of the Russian Federation and Ukraine announced this morning in Moscow," said Czech Industry Minister Martin Riman, whose country holds the EU presidency." "However, we remain realistic," Riman said in a statement. "Over the past few days we have seen several similarly hopeful moments. The only thing that counts for the EU is the resumption of gas supplies. For the time being it is not clear when this resumption takes place." Analysts described the gas deal outlined by Putin and Tymoshenko as a nominal victory for Russia, but one that came at a high price for both sides. "The toll on Russia's reputation as a credible supplier of energy is huge," said Maria Lipman, a political analyst at the Carnegie Moscow Centre. Ukraine agreed to shift to full European prices for Russian gas in 2010 after years of enjoying significantly lower prices than those paid by Russia's European customers. But in 2009 Ukraine would get a 20-percent discount on the European price, as long as it kept the tariffs it charges for transiting Russian gas to Europe at the 2008 level, Putin said. Even with the discount, Ukraine will pay much more for gas than it did last year. In 2008 Ukraine paid 179.5 dollars per 1,000 cubic metres of gas from Russia while the average price in Europe was over 400 dollars. Gas prices in Europe are now around 450 dollars per 1,000 cubic metres. In the longer term however the price of gas is expected to fall since it is indexed to the price of oil, and crude prices have plunged in recent months due to the global economic slowdown. The actual price that Ukraine would pay for gas in 2009 remained unclear as was whether the two sides had settled a dispute over Ukraine's unpaid debts from 2008. It was also unknown whether Tymoshenko's deal with Putin would be supported by her political arch-rival at home " President Viktor Yushchenko, who has taken a harder line with Russia than she has. The Ukrainian presidency withheld its final judgement on the deal with presidential energy advisor Bohdan Sokolovsky saying the negotiating was not yet finished