NYPD officers place metal barricades outside of Trump Tower on March 21, 2023 in New York City. AFP
The ex-president himself claimed he would be "arrested" on Tuesday over hush money paid to a pornographic actress, but his lawyer said the comments were based on media reports and not any fresh action by prosecutors.
Some US media speculated that the grand jury hearing the case could vote to indict on Wednesday but that it may be next week before Manhattan District Attorney Alvin Bragg announces any charges.
Bragg, an elected Democrat, has not confirmed any plans publicly and grand juries operate in secret to prevent perjury or witness tampering before trials, making it virtually impossible to follow their proceedings.
The DA has put key witnesses in front of the panel in recent weeks and offered Trump the opportunity to testify, hinting that an indictment is close.
The 76-year-old Republican would become the first former or sitting president to be charged with a crime if an indictment is filed -- a move that would send shockwaves through the 2024 White House race, in which Trump is running to regain office.
The New York Police Department has geared up for an unprecedented arrest or self-surrender which would see an ex-leader of the United States booked, fingerprinted and possibly even handcuffed, by erecting barricades outside Bragg's office and Trump Tower on Fifth Avenue.
NBC News reported that every NYPD officer has been ordered to wear their uniforms and prepare for deployment starting from Tuesday.
"While you will see an increased uniformed presence throughout the five boroughs, there are currently no credible threats to New York City," an NYPD spokesperson said in a statement.
Trump called over the weekend for mass protests if he is indicted but there has so far been no indication of any large movement. Leading Trump figures such as his sons have not openly urged action in the streets as they did after the 2020 election, when President Joe Biden defeated Trump.
A Monday evening protest in lower Manhattan organized by the New York Young Republican Club attracted only a couple dozen Trump supporters.
Bragg's inquiry centers on $130,000 paid weeks before the 2016 election to Stormy Daniels to stop the porn star from going public about an affair she says she had with Trump years earlier.
Trump's ex-lawyer-turned-enemy Michael Cohen, who has testified before the grand jury, told Congress in 2019 that he made the payment on Trump's behalf and was later reimbursed.
The payment to Daniels, if not properly accounted for, could result in a misdemeanor charge for falsifying business records.
That might be raised to a felony if the false accounting was intended to cover up a second crime, such as a campaign finance violation, which is punishable by up to four years behind bars.
Legal experts say the argument would be difficult to prove in court however, and any jail time is far from certain.
An indictment would begin a lengthy process that could last several months, as the case would face a mountain of legal issues and move toward jury selection.
Trump has denied having had an affair with Daniels and has blasted the investigation as a "witch hunt."
"Our enemies are desperate to stop us because they know that we are the only ones who can stop them," Trump said in a video posted on his Truth Social platform overnight into Tuesday.
He is facing facing several criminal investigations at the state and federal level over possible wrongdoing that threaten his new run at the White House, including his efforts to overturn his 2020 election loss in the state of Georgia.