Fico said, "it's weird" that Ukraine, which has an association agreement with the 28-nation European Union and receives help from the bloc, takes "unilateral steps" that can pose a threat to the economic interests of individual EU nations.
The Slovak president said that EU officials should deal with sanctions, AP reported.
Slovakia, which almost entirely depends on Russian gas, was among the nations hit hardest by Russia's 2009 cutoff of gas shipments via Ukrainian pipelines to Europe. It fears new energy problems even though the country can now get gas supplies from the West.
Fico also said his country is ready to start gas deliveries to Ukraine from Western Europe through its pipeline starting in September.