Ukraine's foreign ministry said on Thursday that Russian oil destined for eastern Europe and transiting via the Ukrainian part of the Druzhba pipeline had been suspended since January 27 due to a Russian attack.
Fico, who has maintained relations with Moscow after it invaded Ukraine in 2022 and has blamed European partners for prolonging the war by supplying weapons to Kyiv, said oil supplies have become a political issue, but did not provide any evidence to back up his claim.
"We have information that (the pipeline) should have been fixed," Fico told reporters after meeting US Secretary of State Marco Rubio in Bratislava on Sunday.
"I perceive what is happening around oil today as political blackmail toward Hungary due to the uncompromising stance of Hungary on Ukraine's EU membership," Fico said.
He said the pressure was that "if Hungary agrees with EU membership, perhaps oil supplies arrive".
A spokesperson for Ukraine's foreign ministry did not immediately respond to a Reuters request for comment.
Fico's comments echoed Hungarian Foreign Minister Peter Szijjarto, who on Friday accused Ukraine of holding up the resumption of flows.
Slovakia and Hungary have continued to buy Russian gas and oil despite EU efforts to switch to alternative supplies completely, with both countries arguing that their lack of access to sea terminals and alternative routes made diversification difficult and expensive.
Hungary opposes Ukraine's EU entry.
Fico reiterated that Slovakia would agree to it if Kyiv meets all necessary conditions, but he added that countries like Serbia, Albania and Montenegro were much better prepared for membership than Ukraine.
Fico also said he did not believe either side of the Russia-Ukraine conflict and could not say who was responsible for the damage to the pipeline.
"There have been so many lies from one side and the other that I do not have the courage to say who bombed or destroyed part of the oil infrastructure," Fico told reporters.
