Ukrainian President Viktor Yanukovych on Wednesday called a $7 billion bill from Russian gas giant Gazprom unfair, saying he was prepared to negotiate with Moscow.
"We told Gazprom that we think this bill is unfair, and we are ready to further analyse this issue in negotiations with Russia," Yanukovych told journalists through a translator during a visit to Lithuania.
Late last month a high-ranking Ukrainian official source told AFP the ex-Soviet country was "not going to pay" Gazprom the hefty sum.
Ukraine's state energy firm Naftogaz has confirmed it received a stunning surprise bill for $7 billion (5.2 billion euros) from Gazprom, for gas Kiev contracted for but did not buy last year.
The payment dispute risks a new episode in a long string of gas wars between Moscow and Kiev and comes at a time Kiev is bracing for budget trouble amid an economic slowdown.
Yanukovych insisted Wednesday that Russian gas prices for Ukraine "are not calculated objectively" but put the blame on his political rival, jailed former prime minister Yulia Tymoshenko.
"Of course, gas prices are not calculated objectively, it is not fair, but it is the result of the contract signed by the previous government, namely the results of contracts signed by Tymoshenko", he said.
Kiev's prosecution and incarceration of the 2004 Orange Revolution leader on abuse of power charges has caused a major deterioration in ties with the West, where Yanukovych has faced accusations of abusing the courts to eliminate his chief political foe.
The Gazprom bill was presented as the Ukraine signed a landmark $10-billion shale gas production sharing agreement with global oil giant Royal Dutch Shell in Kiev's most ambitious move to limit its dependence on Russian gas.
A dispute between Kiev and Moscow over gas prices and bills in early 2009 prompted Gazprom to cut gas supplies to Kiev and leave parts of Europe without energy amid a bitterly cold winter.
Yanukovych made the comments during a joint Wednesday press conference with Lithuanian President Dalia Grybauskaite, who warned the "EU is keeping a very close eye on the course of the trials of political opponents."
An ex-Soviet Baltic state, Lithuania is gearing up to take over the 27-member bloc's six-month rotating presidency in July.