President Donald Trump's longtime lawyer Michael Cohen is parting ways with his legal team just days before a critical deadline, in a move that could signal a new legal strategy or even a decision to cooperate with prosecutors.

Cohen, who served as a fixer for Donald Trump before he was president, has been under criminal investigation for bank and wire fraud as well as tax issues relating to his taxi business.

Cohen has been represented by lawyer Stephen Ryan, a Washington, D.C. lawyer with the firm of McDermott, Will & Emery.

There was no court filing and no official reasons have been given for the split, first reported by ABC News.

But the sudden move, in advance of a Friday court deadline for going through millions of documents, led to immediate speculation by sources that Cohen would move to cooperate with prosecutors.

That suggestion was denied by Rudy Giuliani, an attorney for Trump, who told Fox News' Laura Ingraham: 'It's not so. He's not cooperating nor do we care because the president did nothing wrong. am absolutely certain of that.'

Michael Cohen, personal lawyer to U.S. President Donald Trump, center, exits federal court in New York, U.S., on Wednesday, May 30, 2018

Giuliani was asked if the Trump team was concerned that Cohen may have tape recordings that exist without their knowledge.

'Michael Cohen I think would tell you he's got nothing incriminating with the president,' he said, adding that the President was 'clean as a whistle'.

There are other possible reasons. A source told the network that among the reasons Cohen is making the change is a dispute over fees as the besieged Trump lawyer contends with skyrocketing costs of of the case.

The firm is expected to no longer represent Cohen going forward reported, unidentified sources told ABC. The sources said they expect Cohen to cooperate.

Michael Avenatti, the lawyer for porn star Stormy Daniels, estimated that Cohen's costs were reaching up to $500,000 per week – 'not a typo,' he wrote on Twitter.

Cohen's break from the firm also includes Ryan's co-counsel, Todd Harrison.

Although there is not evidence of it yet, the split could also be a sign of some unknown friction between Cohen and his lawyers, possibly involving something discovered in the trove of documents seized by the FBI.

Philadelphia trial lawyer Max Kennerly tweeted some other scenarios, including the possibility that 'something found in the raid contradicts what he told his lawyers.'

The investigation and potential charges have put him under tremendous pressure in the Southern District of New York, while special counsel Robert Mueller continues his Russia probe.

The Wall Street Journal confirmed the firm's departure, but said people familiar with the matter said Cohen had not decided whether to cooperate.

The report indicated Cohen wanted to hire a new lawyer with close ties to the Manhattan District Attorney's office.

Ryan is a Washington-D.C. based lawyer.

CNN reported that Cohen has yet to meet with prosecutors to discuss any potential cooperation agreement.

Lawyers have been poring over 3.7 million documents seized in an FBI raid of Cohen's home and office.

Ryan did not immediately return a call seeking comment.

Cohen has been telling friends he expects to be arrested imminently, the New York Daily News reported.

A source told the publication Cohen fears he will get indicted and arrested.

'Trump should be super worried about Michael Cohen,' an official said. 'If anyone can blow up Trump, it's him'

President Trump has branded the probe a 'witch hunt' and acknowledged the pressure Cohen is under.

The potential charges prompted federal agents to raid Cohen's home in Manhattan on April 9.

Federal Judge Kimba Wood has given Cohen's lawyer until Friday to sort through remaining documents seized in the raid. A 'special master' is overseeing the process.

Cohen negotiated a nondisclosure agreement with porn star Stormy Daniels, who claims she had an affair with Trump in 2006. Cohen signed the deal, although Trump, who was identified by a pseudonym, did not. He later reimbursed Cohen for up to $250,000, according to a financial disclosure form.

President Trump blasted the FBI raid on Cohen after it happened.

'It's a real disgrace,' the president told reporters. 'It's an attack on our country in a true sense. It's an attack on what we all stand for.'

Trump tweeted in May: 'Mr. Cohen, an attorney, received a monthly retainer, not from the campaign and having nothing to do with the campaign, from which he entered into, through reimbursement, a private contract between two parties, known as a non-disclosure agreement, or NDA.'

He continued in the pair of tweets: 'These agreements are...very common among celebrities and people of wealth. In this case it is in full force and effect and will be used in Arbitration for damages against Ms. Clifford (Daniels). The agreement was used to stop the false and extortionist accusations made by her about an affair.'

Donald Trump lawyer Michael Cohen and his wife Lauren Cohen were seen out in Tribeca after having lunch at Tribeca Grill in New York City

Trump concluded: '...despite already having signed a detailed letter admitting that there was no affair. Prior to its violation by Ms. Clifford and her attorney, this was a private agreement. Money from the campaign, or campaign contributions, played no roll in this transaction.'

Daniels' real name is Stephanie Clifford.

Cohen has been working for Trump since 2011 in an assortment of roles, earning himself the nickname 'bulldog.'

An ex-White House official shared with Vanity Fair that Trump should definitely be concerned if Cohen turns on him.

'Trump should be super worried about Michael Cohen,' the official said to Vanity Fair. 'If anyone can blow up Trump, it's him.'

Cohen sent a text message to Vanity Fair, asserting that 'your alleged source is wrong!'

The embattled attorney is also under the radar of special counsel Robert Mueller as he works to find links of collusion between Russia and the Trump campaign.

Shortly after Trump's election, a plethora of companies gave millions to Cohen's consulting firm - Essential Consultants.

One such company was Columbus Nova, a Manhattan based investment firm whose primary client is Russian oligarch Viktor Vekselberg.

The latest in the Cohen courtroom saga is that a federal judge ruled on Friday that Trump would have to publicly object to documents he seeks to have protected from prosecutors' examination, according to the New York Post.

Retired judge Barbara Jones is combing through the materials obtained by agents in their search and seizure of items at Mr. Cohen's law office and home on April 9.

Her role is to root out any documents that might be protected under lawyer-client confidentiality between Trump and Mr. Cohen.

Jones' first report, issued on June 4, indicated that only a small portion of the documents she had reviewed up until now are protected by privilege.

Trump's attorney in the matter, Joanna Hendon, had hoped to make her case privately to Judge Kimba Wood as to why at least one designation was inaccurate.

'The submissions at issue will disclose matters pertaining to privilege and the grand jury investigation, exclusively,' Hendon wrote.

Prosecutors opposed the objections being made privately, and Wood sided with the state.

'(The) objections should be filed publicly, except for those portions that divulge the substance of the contested documents,' Wood wrote.

President Donald Trump's long-time personal attorney Michael Cohen exits a New York court on April 16, 2018 in New York City, accompanied by attorney Stephen Ryan

Stormy Daniels attorney Michael Avenatti jumped on the report, and went after Cohen's counsel. Avenatti himself stepped back from the New York case after the judge warned the California lawyer he couldn't get dispensation to handle the case while also going on a publicity tour.

'So after Mr. Ryan makes false accusations against me in fed court, he now abandons Mr. Cohen, withdraws, tucks his tail between his legs, & goes home? Just like David Schwartz before him!! Not a good look and a disaster for Mr. Cohen and Mr. Trump. #Basta' Avenatti tweeted.

After the feds raided Cohen, Trump blasted the move on Twitter. 'Attorney-client privilege is dead!' Trump wrote.

The president cast it as an attack on the country, although other observers said it could put pressure on Trump in the Russia probe. Cohen represented Trump in a series of business and personal matters beyond the Daniels case. He was involved in talks with Russians over a potential Trump Tower Moscow during the presidential campaign.

'It's an attack on our country in a true sense. It's an attack on all we stand for,' Trump said after the raid. 'That is really now on a whole new level of unfairness.'