MINSK, June 23 (RIA Novosti)-Russia's industry and energy minister said Friday that Ukraine should be fulfilling the terms of natural-gas deals with Russia rather than trying to revise them.

Ukraine's prime minister in waiting, Yulia Tymoshenko, said Thursday that she would seek to achieve lower prices for Russian and Central Asian gas once she returned to the premier's chair.

"All agreements on gas supplies to Ukraine today call for further profound revision, and for construction in a friendly mode of new contractual relations with Russia and Turkmenistan," she said.

However, Russian minister Viktor Khristenko responded robustly Friday, saying energy giant Gazprom had signed a deal with Ukraine for five years and for supplies to Europe.

"The first thing that must be done is to honor the agreements," the minister said. "Statements about reviewing them can only be made when they [the deals] expire."

"Agreements are not written and signed so they can be reviewed but so they can be fulfilled," Khristentko said.

A Gazprom spokesman reacted to Tymoshenko's comments Thursday with a strongly worded statement.

"We believe that Yulia Tymoshenko's words again prove that Ukraine is regrettably the weak link in the chain of Russia's gas supplies to Europe," Sergei Kupriyanov said, saying Tymoshenko's threats could lead to a new crisis similar to the one that hit Ukraine-Russian relations at the start of the year.

In January, Gazprom cut off supplies to neighboring Ukraine after it refused to agree to a new price for supplies of Russian natural gas. Gazprom clients in Europe registered a shortfall shortly afterward as the Russian energy giant accused Ukraine of siphoning off European-bound gas.