Former White House National Security Advisor Michael Flynn leaves the Prettyman Federal Courthouse following a sentencing hearing in U.S. District Court December 18, 2018 in Washington, DC.

"In an extraordinary reversal, the defendant now claims that he is innocent of the criminal charge in this case," prosecutors wrote.

Flynn "makes this claim despite having admitted his guilt, under oath, before two federal judges (including this Court)," prosecutors said in their new filing in U.S. District Court in Washington, D.C.

Federal prosecutors on Tuesday blasted an "extraordinary" claim by President Donald Trump 's first national security advisor Michael Flynn — who had pleaded guilty to lying to the FBI — that he is the victim of a "plot to set up an innocent man."

In their filing, prosecutors continued to brush aside allegations by Flynn's legal team that they are withholding information that could exonerate him.

And they argued that it was procedurally improper for Flynn's lawyers to raise a new claim of innocence in a filing that is asking for something else — purported evidence in the case.

The dispute could, yet again, upend plans for Flynn's criminal sentencing, which is set for Dec. 18, as of now at least.

Flynn almost two years ago pleaded guilty to lying to the FBI about what he discussed with then-Russian ambassador Sergey Kislyak before Trump's inauguration in January 2017.

Flynn was prosecuted by then-special counsel Robert Mueller during Mueller's investigation of Russian meddling in the 2016 election.

As part of his plea deal, Flynn agreed to cooperate with the Mueller probe.

Flynn nearly was sentenced last December — but the hearing for his punishment was aborted shortly after it began.

At that hearing, Flynn got a tongue-lashing from Judge Emmet Sullivan, who indicated he might impose a stiffer sentence on Flynn than either Mueller's team of prosecutors or his original defense lawyers had anticipated.

Flynn then agreed to Sullivan's suggested postponement of the hearing, to give Flynn time to complete his cooperation with prosecutors.

In June, Flynn hired a new lawyer, Sidney Powell, who has been a harsh critic of Mueller.

Powell since then has filed multiple motions with the court, asking for prosecutors to turn over documents and other evidence that she has argued would cast doubt on the case against Flynn.

Powell so far has not formally asked Sullivan to dismiss the case.

But in September, she said she would make such a request if prosecutors continued to claim that they did not have such exculpatory material.

Last week in a filing, Powell said, "As new counsel has made clear from her first appearance , Mr. Flynn will ask this Court to dismiss the entire prosecution based on the outrageous and un-American conduct of law enforcement officials and the subsequent failure of the prosecution to disclose this evidence — which it had in its possession all along either in a timely fashion or at all."

In the same filing, she accused the FBI of orchestrating "an ambush-interview ... for the purpose of trapping [Flynn] into making statements they could allege as false."

"When the Director of the FBI, and a group of his close associates, plot to set up an innocent man and create a crime ... this amounts to conduct so shocking to the conscience and so inimical to our system of justice that it requires the dismissal of the charges for outrageous government conduct," Powell wrote.

On Monday, Sullivan canceled a hearing originally scheduled for Nov. 7, during which the parties were expected to discuss their dispute over the materials that Powell is requesting.

In their new filing, prosecutors ask Sullivan to explain why he scrapped that hearing.

"It may be that the Court intends to strike any arguments or claims raised for the first time by the defendant in his Reply," prosecutors wrote.

"And it may be that the Court plans to require the defendant to raise any new claims for relief in a properly pled motion to which the government can respond fully."