Russia's President Dmitry Medvedev speaks during a meeting at Russia's Black Sea resort of Sochi, January 8, 2009.

MOSCOW, Jan. 11 (Xinhua) -- Russia will not apply a protocol on gas transit to its clients in the European Union until Ukraine retrieves its additional conditions in the contract, President Dmitry Medvedev said on Sunday.

"Such reservations and additions are nothing but mockery of common sense and violation of earlier agreements. In fact, they aim to thwart gas transit control," Itar-Tass news agency quoted Medvedev as saying during a meeting with Foreign Minister Sergei Lavrov.

Russia and the EU, in a step toward resuming Russian gas supplies to Europe, on Saturday signed a protocol to set up an international commission to monitor Russian gas transit via Ukraine.

Russia supplies about one-quarter of the EU's natural gas, and some 80 percent of it is transported through Ukraine. However, it cut off gas supplies to Ukraine on Jan. 1 after the two sides failed to reach a new deal for 2009 and debt repayments.

All Russian gas supplies to Europe via Ukraine were shut down last Wednesday as the gas row escalated, creating supply crisis for a number of EU countries, mostly in Central and Eastern Europe.

The EU has urged Russia to resume pumping gas to the 27-nation bloc via Ukraine immediately after a monitoring deal was finally clinched.