Pellegrini, who under the constitution calls election dates, said the first round would be held on March 23, and the second round runoff, to be held in the likely case that no candidate wins outright majority, on April 6.

The vote is likely to be a showdown between the ruling coalition led by Prime Minister Robert Fico and independent candidates who are closer to the liberal opposition.

The EU and NATO country's presidents do not wield much day-to-day power, but they can veto laws or challenge them in the constitutional court. A victory by Pellegrini, leader of the government Hlas (Voice) party, would solidify the coalition's grip on power.

"If the party leadership agrees my candidacy and all requirements are met, then...I will announce my candidacy on Jan. 19," Pellegrini said after announcing the election dates at a news conference.

Main opponents so far are former foreign minister in the previous government Ivan Korcok, 59, and an international diplomat and foreign minister from Fico's past more pro-western era, Jan Kubis, 71.

Opinion polls have shown Pellegrini, 48, would have an edge over others in a hypothetical second round. Further candidates may yet appear, including from nationalists in the government camp.

Fico, who has turned anti-western and opposes military aid to Ukraine, formed a government coalition with former party ally Pellegrini and the nationalist SNS party after winning a September 2023 parliamentary election.

The new government has halted official military aid to Ukraine, and has started pushing through a fast-track reform of the criminal law and prosecution that raised worries in the European Union and the United States for potentially weakening the rule of law.

Presidents can slow down legislation by using vetoes, and can also turn to the constitutional court to question adopted laws - tactics Caputova has used against past and current governments.

Slovak presidents are elected for five years, and can seek two consecutive terms, which the human rights lawyer Caputova will not. She has frequently been criticised for her liberal stance by Fico, who has alleged, without proof, she was a U.S. puppet and served the interests of U.S. financier George Soros.

(Reporting by Jan Lopatka in Prague; Editing by Angus MacSwan)

By Jan Lopatka