A federal judge on Monday indefinitely postponed the sentencing date for President Trump’s former national security adviser Michael Flynn on charges of lying to the FBI in the Russia investigation.

The move by Judge Emmet Sullivan comes a day after federal prosecutors filed a rare Sunday motion to delay a number of approaching deadlines that would ultimately make Flynn’s Feb. 27 sentencing unlikely. The delay also comes weeks after Flynn withdrew his guilty plea.

In their filing, prosecutors argued that Flynn’s former attorneys should testify after he claimed to have received ineffective assistance from them. Flynn had previously hired the premier D.C. law firm, Covington & Burling. Federal lawyers also asked the judge to order that Flynn has his attorney-client privileges in his communications with Covington & Burling waived.

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“The government requests that the Court suspend the current briefing schedule concerning the defendant’s [motion] until such time as the government has been able to confer with Covington regarding the information it seeks,” prosecutors wrote. “While Covington has indicated a willingness to comply with this request, it has understandably declined to do so in the absence of a Court order confirming the waiver of attorney-client privilege.”

Flynn in January moved to withdraw his guilty plea for lying to the FBI in the Russia probe, citing "bad faith" by the government. That court filing came just days after the Justice Department reversed course to recommend up to six months of prison time in his case, alleging he was not fully cooperating or accepting responsibility for his actions.

"The prosecution has shown abject bad faith in pure retaliation against Mr. Flynn since he retained new counsel," Flynn’s attorneys wrote in the filing. "This can only be because with new, unconflicted counsel, Mr. Flynn refused to lie for the prosecution."

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Flynn's case stemmed from a 2017 FBI interview, in which he was asked about his conversations with former Russian Ambassador to the U.S. Sergey Kislyak. Flynn ultimately pleaded guilty to making false statements regarding those conversations during his interview, as part of former Special Counsel Robert Mueller’s Russia investigation.

Judge Sullivan in December rejected claims from Flynn's lawyers that he was pressured to plead guilty to lying to federal investigators about his contacts with the Russian diplomat.

Fox News’ William Mears contributed to this report.