The two countries' energy companies, Russia's Gazprom and Ukraine's Naftogaz, signed a gas supply and transit contract on January 19 following negotiations between Russian Prime Minister Vladimir Putin and his Ukrainian counterpart, Yulia Tymoshenko.
"The prime minister was not authorized to make the decisions taken as part of the Moscow agreements [on gas supplies]," Yushchenko said.
The Ukrainian president also said that the deal "directly threatens the independence of Ukraine."
Russia suspended supplies to Ukraine on January 1 after the former Soviet neighbors failed to reach an agreement on a new gas contract for 2009. A week later, Gazprom cut off gas deliveries to the European Union, saying Ukraine was stealing gas intended for EU consumers.
Under the terms of the new gas deal, Ukraine will have to pay Russia $450 per 1,000 cu m with a 20% discount in 2009 while transit fees have not been revised.
On Monday, Yushchenko said that, "This is obviously unfair. I'm sure that those who have signed this agreement and accepted these terms will have to answer for their actions."
He said $450 was "an exorbitant price."
A Ukrainian presidential representative said on Saturday that Naftogaz could go bankrupt as a result of the deal on gas prices agreed with Moscow.
This is not the first time that Yushchenko and officials in his administration have slammed the terms of the deal.
Ukraine's prime minister, however, said on Tuesday she would turn to the European Union for a probe into contracts on gas deliveries to Ukraine and its transit to Europe.
"I will literally tomorrow address an official letter to the European Union and request a probe into the contracts we signed, and I am sure their conclusion will corroborate everything I am speaking about," Tymoshenko said.
