Cohen, now with no legal representation, is likely to cooperate with federal prosecutors in NY, sources said.
A retired judge is reviewing more than 3.7 million items seized in the Federal Bureau of Investigation search to determine whether they should be held back from investigators because they are privileged attorney-client communications or are personal.
Cohen has maintained that he's innocent of wrongdoing, and Trump has called the raid on his lawyer an assault on attorney client privilege.
The split could signal a shift in legal strategy and comes amid mounting pressure on Cohen as criminal charges could become likely.
"It would be a conflict right now for him to be the president's attorney", Giuliani said on ABC's "This Week With George Stephanopoulos".
The firm's spokesperson did not immediately respond to requests for comment.
WH adviser Navarro apologizes for 'special place in hell' slam at Trudeau
The sentiment was echoed by two of the president's top advisers on Sunday , who claimed Trudeau stabbed the U.S.in the back. Russian Federation was thrown out of the group in 2014 over the annexation of Crimea.
Stephen Ryan and Todd Harrison of the law firm McDermott, Will & Emery LLP were representing Cohen during a legal battle regarding the seizure of Cohen's files in Federal Bureau of Investigation raids of his home, hotel room, and office.
The seized documents related to several matters, including Trump's payment to porn star Stephanie Clifford, who goes by Stormy Daniels.
Cohen has denied any wrongdoing related to the Russian Federation investigation, and in the case playing out in the Southern District of NY.
While Cohen has not been charged with a crime, he is the subject of an investigation by federal prosecutors of alleged wire fraud and other crimes.
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