Prosecuting Donald Trump would be a politically motivated move by his opponents, senior Republicans say.
Ednews reports citing CNN that on Saturday, the former US president said his arrest could happen next week, based on media reports.
But Democrats have said no-one is above the law and accused Mr Trump of recklessly stoking political divisions.
The case focuses on alleged hush money paid on Mr Trump's behalf by his lawyer to porn star Stormy Daniels ahead of the 2016 presidential election.
The 76-year-old is also the subject of several other separate inquiries, although he has not yet been charged in any and denies wrongdoing.
Mr Trump has pledged to continue his campaign to become the Republican nominee in the 2024 presidential election, even if he is indicted.
It is not yet known if he is going to be criminally charged or even, beyond the most basic details, what any indictment might contain.
