America readied itself Monday ahead of the possible historic indictment of Donald Trump over a hush-money case, with the former president calling for mass demonstrations if he is charged.

Trump supporters were scheduled to protest in New York later Monday as Manhattan district attorney Alvin Bragg weighs charging the ex-president over a payment to porn actress Stormy Daniels in 2016.

Trump would become the first former or sitting president to ever 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.

Bragg, an elected Democrat, has not confirmed any plans to indict, but has indicated that prosecutors are nearing a decision by putting key witnesses in front of a grand jury in recent weeks and offering Trump the opportunity to testify.

The 76-year-old former Republican president said over the weekend that he expects to be "arrested" on Tuesday and urged supporters to "Protest, take our nation back!"

"They are MANY years beyond the Statute of Limitations which, in this instance, is TWO YEARS. More importantly, THERE WAS NO CRIME!!!" Trump wrote on his Truth Social platform Monday.

Law authorities are gearing up for an unprecedented arrest that would see an ex-leader of the free world fingerprinted and possibly even handcuffed.

More than a dozen senior New York officials met with senior safety aides of city mayor Eric Adams on Sunday to discuss security and contingency plans for any protests, the New York Times reported.

NBC News said that police and other law enforcement agencies had conducted "preliminary security assessments," including placing a security perimeter around the Manhattan Criminal Court where Trump would likely appear before a judge.

"The NYPD's state of readiness remains a constant at all times, for all contingencies. Our communications and coordination with our partners in government and in law enforcement are fundamental tenets of our commitment to public safety," a police spokesperson told AFP.

Senior Democrats have warned that Trump's calls could trigger a repeat of the violence that his supporters unleashed on the US Capitol in January 2021.

The New York Young Republican Club announced a "peaceful protest" of Bragg's "heinous attack" on Trump for 6:00 pm (2000 GMT) in lower Manhattan Monday but it was unclear how many would turn out.

Trump has blasted the investigation as a "witch hunt," while his vice-president Mike Pence described the probe as a "politically charged prosecution."

Trump's many legal woes

Bragg's inquiry centers on $130,000 paid weeks before the 2016 polls to stop Daniels from going public about an affair she says she had with Trump years earlier.

Trump's ex-lawyer-turned enemy Michael Cohen alleges that he made the payment 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.

Cohen testified in front of the grand jury last week while Daniels is cooperating with prosecutors.

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, whose real name is Stephanie Clifford.

He is facing several criminal probes at state and federal level over possible wrongdoing that threaten his new run at the White House.

In Georgia, a prosecutor is investigating Trump and his allies' efforts to overturn his 2020 election loss in the southern state. The grand jury in that case has recommended multiple indictments, the forewoman revealed last month.

The former president is also the subject of a federal probe into his handling of classified documents as well as his possible involvement in the January 6 rioting.

Some observers believe an indictment bodes ill for Trump's 2024 chances, while others say it could boost his support.