By Yuliia Dysa

(Reuters) - Ukrainian President Volodymyr Zelenskiy discussed energy security with Slovakia's opposition leader in Kyiv on Friday, amid a row with Slovak Prime Minister Robert Fico who has threatened to cut aid to Ukraine.

Fico is angry with Kyiv over its decision not to extend a deal on the transit of Russian gas supplies via Ukraine, saying the move had damaged Slovakia's economy. His leftist-nationalist coalition is looking shakier and faces a no-confidence vote.

Zelenskiy had invited Fico to visit Kyiv for talks on Friday, an invitation he alluded to as he announced his meeting with Michal Simecka, the head of Progressive Slovakia, the country's biggest opposition party.

"Friday. Expected one Slovak leader, but met another. I had a good meeting with Slovak parliamentarians, led by @MSimecka," Zelenskiy wrote on X.

"We are ready for an open and mutually beneficial dialogue on all issues, particularly in the energy sector. This dialogue must strengthen our nations — Ukraine and Slovakia — not Moscow," Zelenskiy said in his statement after meeting Simecka.

Simecka said in a separate statement that he believed Ukraine was ready to negotiate over the issue, adding: "That is exactly what I am calling on Robert Fico to do now".

Russian gas flows to Europe via Ukraine ended at the start of the year after the transit agreement between Kyiv and Moscow expired. Kyiv refused to extend the deal to reduce revenue streams supporting Russia's war in Ukraine.

The overall gas situation has remained stable in Slovakia, but Fico says the end of Russian gas supplies via Ukraine has resulted in higher gas prices and a loss of transit fees. He has insisted on the need to restore flows, something Kyiv rejects.

THREATS

Zelenskiy and Fico have since exchanged mutual accusations.

If the gas transit problem is not resolved, Fico has threatened to cut emergency electricity supplies to Ukraine, reduce aid for its refugees in Slovakia or to use its veto right on European Union decisions relating to Kyiv.

Zelenskiy has said Fico's lack of desire to reduce his country's dependence on Russian natural resources threatens both Slovakia and Europe.

On Monday, Fico proposed he and Zelenskiy meet on the Slovakian-Ukrainian border to discuss the gas situation. Zelenskiy said Fico should instead come to Kyiv for the talks.

Fico said on Thursday that he was looking for a date to meet Zelenskiy, which could happen in the "nearest days", according to Slovak media.

He did not give details, but both leaders are scheduled to attend the Davos forum in Switzerland in the coming week.

(Reporting by Yuliia Dysa, additional reporting by Jan Lopatka; Editing by Tom Balmforth and Gareth Jones)