Manhattan District Attorney Alvin Bragg sought to reassure his staff in an internal message that intimidation or threats against them would not be tolerated. The communication comes as his office moves forward in its investigation into former President Donald Trump, who said Saturday that he believes he will be arrested on Tuesday and put out a call for his supporters to protest.

"Please know that your safety is our top priority," Bragg said in a memo to office staff obtained by NBC News from a senior official at the Manhattan DA’s office.

He added, "We do not tolerate attempts to intimidate our office or threaten the rule of law in New York."

The letter, which was first reported by Politico, did not mention Trump by name, and referred only to "an ongoing investigation by this office."

Trump predicts his arrest in hush money case and calls for protests

March 18, 202303:30

Trump is under investigation by Bragg's office in connection with a hush money payment made to adult video performer Stormy Daniels during his first campaign for president.

In a post on his social media site Truth Social Saturday, Trump referred to reports that he could face possible criminal charges in the probe and said he believes he'll be arrested Tuesday.

Trump, who’s running for president again, implored followers to protest. “WE MUST SAVE AMERICA! PROTEST, PROTEST, PROTEST!!!” he said on Truth Social.

A spokesperson for Trump later said there hasn't been a notification aside from "illegal leaks" from the Justice Department and "the D.A's office."

Bragg's email did not go into detail about any possible threats to the office, but said law enforcement partners will "ensure that any specific or credible threats against the office will be investigated and that all the proper safeguards are in place."

His office did not immediately respond to a request for comment late Saturday.

NBC News reported Friday that law enforcement agencies are prepping for a possible Trump indictment as early as next week.

Former Trump attorney Michael Cohen is a key witness in the case and testified before the grand jury this week. Cohen pleaded guilty in federal court in 2018 to a federal charge related to making the payment to Daniels. He was sentenced to three years in federal prison for that and other crimes.

Cohen maintains the payment was made at Trump’s direction and that it was for the “principal purpose of influencing” the 2016 presidential election. Daniels has said the two had sex in 2006. The payment was for a nondisclosure agreement, Trump said.

Trump said the payment was legal, and that he repaid Cohen. Trump tweeted in 2018 that the money was “not from the campaign” and that the deal had been “a private contract between two parties, known as a non-disclosure agreement, or NDA.”