Despite EU efforts to reduce dependence on Russian fossil fuels, Slovakia remains reliant on Russian gas under a long-term contract with Russia's state-owned energy giant Gazprom. Switching to alternative supply routes could cost Slovakia an additional €220 million ($229 million) in transit fees.

Slovakia's coalition government will discuss retaliatory measures to take against Ukraine after it halted the flow of Russian gas through its territory to Slovakia, Slovak Prime Minister Robert Fico said on Thursday.

The Urengoy-Pomary-Uzhgorod pipeline was built in the Soviet era to carry Siberian gas to European markets. It became the main conduit to Ukraine’s border with Slovakia from Siberia, passing through the town of Sudzha — which is now under the control of Ukrainian military forces — in Russia’s Kursk region.