Ukraine is aiming to loosen Russia's stronghold over its energy supply by forging a trade deal with European countries to bypass the oil and gas titan.

According to Ukraine's energy minister, the interim government in Kiev began looking for alternative energy suppliers last week after the Russian giant Gazprom almost doubled prices and demanded immediate payment of outstanding gas bills.

The interim government has refused to pay the new tariff set by Russia after dubbing the bill hike as "economic aggression" and "political prices."

Yuri Prodan told the Ukrainian parliament that the European Union would stand by the country if Russia reduced supplies to Ukraine, ensuring that Moscow could bypass Ukraine by moving flows to alternative pipelines.

"Ukraine cannot pay such a political, uneconomic price, so now we are negotiating with the European Union about reverse deliveries into Ukraine," Prodan said.

"We will make gas purchases from reverse flows urgently. On the conditions offered by European gas companies. We plan that they will be Germany's RWE and a French gas company."

The ministry's spokeswoman confirmed the French company is GDF Suez but no agreement has been signed.

Prodan's comments come a day after Russian President Vladimir Putin sent a letter to leaders of 18 European countries, warning that the crisis has become a "critical situation" and that Gazprom may halt supplies to Ukraine unless it agrees to pay for gas in advance at the new price.

The letter warns that if Ukraine did not pay off the $2.2bn (£1.3bn, €1.6bn) in outstanding gas debts, Gazprom would move to an advance payment system. If they still failed to pay.

The company could "completely or partially cut off gas deliveries", it added.

Ukraine's interim government believes that Russia is using its energy supplies as a political tool to punish the country for seeking closer ties with Europe. The US state department also voiced its concerns in the wake of the letter, condemning "Russia's efforts to use energy as a tool of coercion."

Prodan added that Ukraine could obtain small amounts of gas from Poland and Hungary and a larger amount of gas from Slovakia, although he admitted that there would be difficulties in reversing supply through Gazprom pipelines.

Plans to pump gas from EU countries to Ukraine against the original flow of the pipeline may require approval from Gazprom.

Speaking earlier this week, a spokesman for Slovakia's pipeline operator Eustream, said that the move would require permission from Gazprom.

"For a reverse flow, you would have to stop the East-West flow in one of the pipelines and reverse the flow. But you would have to have approval from Gazprom," the spokesman said.

"Gazprom does not agree with this, and thus it's not an option," he added.

Slovakia has called for a meeting with Ukraine, Russia and the European Commission, to make sure it can reverse gas to Ukraine without breaching its existing contracts.