Opposition parties had delayed the vote on whether to fast-track the criminal law reforms for weeks, looking to slow Prime Minister Robert Fico's changes that they argue will afford impunity for politicians and business leaders linked to him.

Pushing the reforms on a faster track has also raised warnings from the European Union and United States.

Opposition parties have led near weekly protests drawing tens of thousands, with more rallies planned for Thursday evening.

The leftist government led by four-time Prime Minister Fico says the changes will end what it calls excesses at the Special Prosecution Office (USP) which he has accused of bias against his party.

Fico has also argued that sentences are too harsh compared with many European countries.

Fico defended the plans while saying the government was ready to table amendments suggested by the EU executive European Commission or Slovakia's general prosecutor.

"But these proposals will not change anything toward the basic fundamental change to the criminal code, criminal procedure and the plan to cancel the office of the special prosecutor," Fico told a news conference broadcast on his Facebook page.

Putting the bills in a fast-track procedure shortens the debate, making a vote possible next week.

President Zuzana Caputova has said speeding through the changes is unprecedented.

The proposed reforms would allow suspended sentences for many more financial crimes, and shorten the statute of limitations, which Caputova said would exonerate many suspects of crimes under investigation or on trial now.

The Commission and the United States have raised objections to hasty reforms, worried about their impact on the rule of law - an issue that has pitted central European neighbours Hungary and Poland against Brussels in recent years.

Fico won a September election and returned to power after he had resigned in 2018 amid mass street protests that followed the murder of a journalist investigating public corruption.

The USP opened a number of cases against business leaders, members of the judiciary and police following a 2020 election victory by parties promising to fight graft. While in opposition, Fico himself faced police charges which were later dropped.

(Reporting by Jason Hovet and Jan Lopatka in Prague; Editing by Nick Macfie)