Ivan Korcok, a pro-Western diplomat and former foreign minister, is hoping to ride a wave of support energised by his first-round victory to edge out government party candidate Peter Pellegrini in Slovakia's presidential election run-off on Saturday.

Korcok, 59, surprisingly won the first round two weeks ago over Pellegrini, 48, on pledges to be a counterbalance to the government of Robert Fico, which has taken a pro-Russian stance on Ukraine and launched reforms criticised for weakening the rule of law.

Final opinion polls ahead of a moratorium on polling showed a dead heat.

NMS agency poll for news website www.sme.sk on Wednesday showed Korcok leading 51.7% to 48.3%, while a poll by Focus agency for TV Markiza on Tuesday showed Pellegrini ahead with 50.8% to 49.2%.

"We will decide on Saturday whether we maintain a balance of powers or allow the government camp to also take the last constitutional post," Korcok said in a campaign video on Wednesday.

Slovak presidents do not have many executive powers, but can veto laws or challenge them in the constitutional court. They nominate constitutional court judges, which may become important in upcoming battles over Fico's reforms of criminal law that would dramatically ease punishments for corruption.

Presidents, like the outgoing pro-western liberal Zuzana Caputova who did not seek a second five-year term, also represent the country at various forums abroad.

Pellegrini backed Fico's turn to what he calls "sovereign" foreign policy, meaning Slovakia remains an EU and NATO member but takes its own course in relations with Russia and others.

"Slovakia should not be merely a passive receiver of what is dictated in Washington and Brussels," Pellegrini said in a television debate on Tuesday.

Pellegrini said he promoted...