The former human rights lawyer won her first five-year term in 2019 and has been a strong voice in favour of European integration, minority rights and a supporter of neighbouring Ukraine in its defence against Russia.

On Tuesday, she said she had to estimate her strength to take on another term.

"With my decision not to run, I am not giving up the ideal and trust in values that I have dedicated my professional and personal life to," she said.

"I tried to help democracy and justice in Slovakia before my presidential mandate, during it, and I will do so after."

Caputova's announcement may prompt other potential candidates to declare they will run. So far, several largely fringe figures have declared interest.

Slovak presidents do not wield many executive powers but have a strong role in forming governments and shaping public debate.

The central European country, a member of the euro zone, faces a snap parliamentary election in September and a presidential vote in March next year.

Caputova is the most popular Slovak politician, with a confidence rating of 42.9%, ahead of opposition leader Peter Pellegrini at 36.3%, according to a poll by the IPSOS agency for news media www.dennikn.sk on Tuesday.

Caputova, 49, has frequently been criticised for her liberal stance by opposition leader and former prime minister Robert Fico, who has claimed, without proof, she was a U.S. puppet and stood for interests of U.S. financier George Soros.

Caputova said last month she would take legal action against Fico, whose Smer party leads opinion polls, for what she called lies. She has said that both she and her family have been a target of death threats.

(Reporting by Jan Lopatka in Prague; Editing by Alex Richardson and Christina Fincher)