In a fast-escalating crisis Friday night, Attorney General William Barr tried to oust Geoffrey Berman, the powerful US attorney for the Southern District of New York who has investigated a number of associates of President Donald Trump, but Berman defied him by refusing to step down.

In an extraordinary statement, Berman said he learned of his exit from a press release."I have not resigned, and have no intention of resigning, my position, to which I was appointed by the Judges of the United States District Court for the Southern District of New York.

I will step down when a presidentially appointed nominee is confirmed by the Senate," Berman said. "Until then, our investigations will move forward without delay or interruption."

Berman's rebuttal came about an hour after the Department of Justice announced Trump intends to nominate Jay Clayton, the chairman of the Securities and Exchange Commission, who has never been a prosecutor.

A Justice Department official told CNN that Berman was offered other positions at Justice, including the head of the civil division, where assistant Attorney General Jody Hunt abruptly announced his departure this week. Berman declined.

A second source with knowledge of the matter said Berman was asked to resign and refused. Attorney General William Barr asked Berman to resign in an in-person meeting in New York on Friday, the source said.

Any forced ouster of Berman is likely to draw scrutiny inside the US attorney's office and among career prosecutors. He has been the US attorney for Manhattan since 2018, and under his leadership, his office prosecuted Trump's former attorney Michael Cohen, is investigating top Trump confidante Rudy Giuliani and indicted the former New York mayor's associates Lev Parnas and Igor Fruman.

Tensions between the New York and Washington offices have grown with Berman and Barr butting heads over the handling of some cases, including the indictment of Turkish bank Halkbank.

Last fall, Justice Department officials discussed replacing Berman with Ed O'Callaghan, a senior official, but then prosecutors indicted the Giuliani associates, a move that appeared to extend Berman's tenure.

The timing of the move, announced shortly before 10 p.m. ET, immediately raised questions about the circumstances regarding Berman's departure.

Preet Bharara, a CNN senior legal analyst who was fired by Trump as US attorney for the Southern District shortly after Trump took office in 2017, told CNN's Don Lemon that the late-night announcement was a "highly irregular thing to do ... when there are all sorts of investigations swirling around."

"The President, his associates, there may be anger about the way that some of the prior investigations were conducted, with respect to his former lawyer Michael Cohen and others," he added.

And Senate Minority Leader Chuck Schumer said the "late Friday night dismissal reeks of potential corruption of the legal process. What is angering President Trump? A previous action by this U.S. Attorney or one that is ongoing?"

Before Clayton was nominated to the SEC post by Trump, he was a corporate lawyer at Sullivan & Cromwell. If confirmed, Clayton would be the first non-prosecutor to lead SDNY.

Barr and Clayton have known each other for years, the Justice official said, and Clayton was planning to leave to go back to NY. He expressed interest in the SDNY job, the Justice official said, and Barr agreed.

Barr said Trump has appointed Craig Carpenito, currently the United States Attorney for the District of New Jersey, to serve as the acting United States attorney for the Southern District of New York until Clayton is confirmed. Carpenito will begin the role on July 3.