Moscow - Russia and Ukraine were set to iron out the final details Monday on an accord to end a 12-day halt on gas deliveries to Europe, but the European Union remained sceptical as it counted the economic costs of the crisis.

Ukrainian Prime Minister Yulia Tymoshenko is expected back in Moscow on Monday for the signing of the agreement she negotiated with her Russian counterpart Vladimir Putin in talks that ran into the early hours of the morning.

Russia and Ukraine's state gas monopolies Gazprom and Naftogaz Ukrainy were working out the final details of the new contract on pricing and transit of gas through Ukraine.

But doubt was rife among analysts that the breakthrough deal - the second announced amid mounting EU pressure - was the end of the so- called "gas war" that has disrupted flows of gas to Europe from January 1.

"While we welcome the provisional resolution ... following the collapse of last week's agreement to resume exports, we reserve judgment until the gas actually starts flowing," Unicredit said in a note to investors Monday.

In a joint statement after five-and-a-half hours of talks, Putin and Tymoshenko said gas flows to Europe would resume "very shortly" once the deal was signed.

The European Commission welcomed the news guardedly, saying the real "test" would be whether gas flows reached Europe of not. "We have seen many false dawns," it said.

Under the anticipated deal, Ukraine will pay European prices for Russian gas deliveries from 2010, but with a 20-per-cent discount for deliveries this year in return for keeping transit fees at 2008 prices.

This puts the price Ukraine would pay for gas at around 230 dollars for 1,000 cubic metres of gas, industry experts said, with the price of gas expected to fall based on its peg to oil.

Russia cut gas to Ukraine after it refused to pay a fixed price of 250 dollars - a huge increase on the 179.50 dollars it paid last year.

Putin and Tymoshenko stayed mum on the exact price Ukraine will pay for gas this year, and there was no mention of an outstanding 614-million-dollar debt for late payments claimed by Gazprom, which Kiev rejects.

Analysts say it will be difficult for Ukraine to swallow the higher energy prices as its economy hangs on the brink of bankruptcy, relying on a 16.4-billion-dollar loan from the International Monetary Fund. (dpa)