The leaders of two gas-starved European nations travelled to Ukraine and Russia on Wednesday, pressing them to restore supplies as the EU threatened both nations with legal action for halting energy deliveries in the middle of a bitter winter.

But Ukraine's natural gas company said for a second straight day it would not send Russian gas along to Europe, citing what it claimed were onerous conditions set by Russia's gas monopoly Gazprom.

With no end to the politically charged dispute in sight - despite an agreement that sent teams of EU monitors out to pumping stations to keep tabs on the gas flows - the EU was fed up.

European Commission President Jose Manuel Barroso warned Gazprom and Naftogaz, Ukraine's state-run gas company, that he will recommend the European energy companies sue them unless they move quickly to restore gas supplies. He insisted that European consumers should not be held hostage to a dispute between energy suppliers.

"If the agreement is not honored, it means that Russia and Ukraine can no longer be considered reliable partners for the European Union in matters of energy supply," Barroso told the European Parliament.

Gazprom stopped sending gas into Ukraine's pipeline system on Jan. 7, alleging that Ukraine was siphoning off supplies destined for Europe. Ukraine has denied the charges, claiming that Russia has not sent enough so-called "technical gas" to pump the rest of the gas west to Europe.

Gazprom cut off all gas supplies to Ukraine itself on Jan. 1, amid a dispute over what price Ukraine should pay for gas in 2009.

The dispute has affected millions of people, mostly in eastern Europe and sent at least 15 European nations scrambling for heat. Thousands of businesses have had to shut down or cut production, forcing workers into involuntary layoffs.

Russia opened a tap to Ukraine on Tuesday after the hard-won EU deal to monitor gas flows, raising hopes across Europe.

But Ukraine's gas company Naftogaz did not deliver the gas to Europe, saying Gazprom demanded that it use a technically arduous route which would force Ukraine to halt supplies to a large swath of its own territory. Ukraine uses Russian gas, but also produces natural gas on its own and has large stockpiles of the fuel.

Naftogaz head Oleh Dubina said Gazprom made the same request again Wednesday - and he would not agree to halt supplies to Ukrainian consumers.
"Unfortunately, we answered the same way: we cannot leave our regions without gas," Dubina told reporters.

Gazprom has rejected the claim, saying the route was fine.

Slovakia and Bulgaria are among the hardest hit in the energy cutoff and their prime ministers traveled to Kiev and Moscow on Wednesday to press their case.

Bulgaria, which depended on Russia for virtually all its gas, has barely two days of reserves. Slovakia has vowed it was ready to restart an aging Soviet nuclear power plant despite EU objections if gas supplies are not restored quickly.

In Kiev, Slovakia's Prime Minister Robert Fico urged Ukrainian Prime Minister Yulia Tymoshenko to hold talks with her Russian counterpart Vladimir Putin to resolve the dispute as soon as possible.

"We ask for talks between the prime ministers of Russia and Ukraine. This is an issue that is very important for us," Fico said.

Fico and Bulgarian Prime Minister Sergei Stanishev were to meet with Putin at his residence outside Moscow later Wednesday.

Russia and Ukraine are deeply at odds over what Ukraine will pay for Russian gas in 2009. Ukraine last year paid $179.50 per 1,000 cubic meters of gas and its president said Tuesday that Ukraine will pay no more than $210 in 2009.

Russia wants Ukraine to pay market price for gas, about the $450 that European customers pay.