Barricades have been erected around a Manhattan courthouse as New York City braces for a possible indictment of Donald Trump over an alleged hush-money payment to a porn star, during his 2016 presidential campaign.

The barriers went up in preparation for what would be the first-ever criminal case against any US president, two days after he urged his followers on social media to protest ‘his looming arrest’.

A grand jury was expected to indict Trump late on Monday or on Wednesday, Politico reported, for arranging payments to porn star Stormy Daniels. Trump, who is seeking the Republican nomination for the White House again in 2024, had predicted he would be arrested on Tuesday.

But on Monday, the grand jury still appeared to be collecting evidence before deciding whether charges were warranted.

According to a source, lawyer Robert Costello was due to appear before the closed-door panel at the request of Trump’s lawyers because he might provide information that would challenge earlier testimony by Michael Cohen, Trump’s former lawyer.

Cohen pleaded guilty in 2018 to federal campaign finance violations tied to his arranging payments to Daniels, whose legal name is Stephanie Clifford, and another woman in exchange for their silence about affairs they claimed with Trump.

Trump has denied that any such affairs took place.

In his call for protests, Trump raised fears that supporters might engage in violence similar to the January 6, 2021, attack on the US Capitol in Washington.

New York Mayor Eric Adams told reporters police were monitoring social media and keeping an eye out for “inappropriate actions” in the city. The New York Police Department said there were no known credible threats.

Trump’s fellow Republicans have widely criticised the probe by Manhattan District Attorney Alvin Bragg as politically motivated.

Florida Governor Ron DeSantis, Trump’s rival for the Republican presidential nomination, said on Monday that Bragg was imposing a “political agenda” that compromised the rule of law, but he also took a veiled swipe at Trump.

“I don’t know what goes into paying hush money to a porn star to secure silence over some type of alleged affair,” he told reporters.

Republicans in the US House of Representatives have launched an investigation of Bragg’s office with a letter seeking communications, documents and testimony related to the probe.

Trump was impeached twice by the House during his presidency, once in 2019 over his conduct regarding Ukraine and again in 2021 over the attack on the US Capitol by his supporters. He was acquitted by the Senate both times.

Meanwhile, laweyers for Trump asked a Georgia court to quash a special grand jury report detailing its investigation into his alleged efforts to overturn his 2020 statewide election defeat.

Trump is also seeking to delay a civil fraud trial, scheduled for October 2, that alleges a decade-long scheme to manipulate the value of his assets to win better terms from bankers and insurers.

The former president also faces two civil trials involving former magazine columnist E. Jean Carroll, who claims that Trump defamed her by denying he raped her. 

An indictment in the hush-money probe could hurt Trump’s comeback attempt. Some 44 per cent of Republicans say he should drop out of the presidential race if he is indicted, according to a seven-day Reuters/Ipsos poll that concluded on Monday.