Slovakia has been trying to preserve Russian gas deliveries via Ukraine in 2025 although Kyiv has refused to renew a transit deal with Moscow expiring at the end of the year while they remain at war, Reuters reported.

Slovakia says alternative routes would sharply drive up costs and hit its own transit operations, causing it to lose €500 million in fees, according to Fico.

In a video message on Facebook on Friday, Fico reiterated his view that the stoppage of gas via Ukraine would hit the EU and its competitiveness.

He cited estimates saying the cost to the bloc could reach €120 billion in 2025–2026 from higher prices for not only the gas but electricity production from the fuel.

He laid the blame on Ukrainian President Volodymyr Zelenskyy, with whom he has publicly argued in the past week.

"After January 1, we will assess the situation and the possibilities of reciprocal measures against Ukraine," Fico said in the video.

"If it is unavoidable, we will halt the electricity supplies that Ukraine needs during grid outages. Or we will agree on a different course of action."

Ukraine has said it will cease to allow Russian gas to flow across its territory from January 1, Reuters reported.

Slovakia has said the move would not hit its consumption demands because of storage capacities, while the country's main gas buyer, SPP, has contracts for the purchase of gas from a non-Russian source with BP, ExxonMobil, Shell, Eni and RWE.

Fico has shifted Slovakia's foreign policy since taking power just over a year ago, notably by stopping military aid to Ukraine and warming relations with Russia. On Sunday, Fico became only the third EU leader to visit Russian President Vladimir Putin in Moscow since the war started.

However, Slovakia has also provided humanitarian aid to Ukraine and exported diesel fuel and electricity to its neighbor. In January to November this year, Slovakia exported 2.4 million megawatt hours of electricity, a 152% year-on-year increase.