<pre><pre>Trump's former national security advisor, Michael Flynn, requests that the confession of guilt in the Müller case be withdrawn

Michael Flynn, a former U.S. security adviser, will leave the federal court in Washington DC on Monday, June 24, 2019.

Andrew Harrer | Bloomberg | Getty Images

Former national security advisor Michael Flynn officially withdrew his admission of guilt on Tuesday, more than two years after he originally lied to federal agents about his contacts with a Russian diplomat before President Donald Trump took office.

"Michael T. Flynn is innocent," his lawyer Sidney Powell wrote in a 22-page file with the US District Court in Washington, D.C.

Powell wrote that Flynn is withdrawing his plea "because the government is disbelieving, vengeful, and violating the plea agreement". She also asked Judge Emmet Sullivan for a 30-day delay in Flynn's sentencing date, which is currently scheduled for January 28.

Sullivan has yet to sign Flynn's withdrawal. The judge could possibly refuse Flynn's request and uphold the confession of guilt.

Two former federal prosecutors, each of whom had spoken to CNBC, said it was "almost impossible" to get approval to withdraw a federal confession of guilt.

It's "extremely difficult," said one of the former prosecutors. "Otherwise, the system would hang up."

Less than a week earlier, prosecutors had asked Sullivan to keep Flynn in prison for up to six months. They referred to the "seriousness" of Flynn's "offense" and "his apparent failure to take responsibility for his crime".

Prosecutors were outraged by what they called Flynn's "extraordinary" shift to an innocence allegation in late 2019.

Her new recommendation to wait half a year was a clear reversal: The public prosecutor had previously advised Flynn not to serve a prison term because of his extensive help in several investigations after his admission of guilt at the end of 2017.

Flynn was indicted by the then special representative Robert Müller as part of the investigation into the Russian election impairment during the 2016 presidential election. He was almost convicted in December 2018, but decided to postpone the proceedings after Sullivan urged him to first end his collaboration with Müller's probe.

"You must have sold your country," said Sullivan at the hearing.

After Sullivan granted this delay in the conviction, Flynn commissioned Powell, who claimed in court files that the prosecutor had suppressed evidence that could prove Flynn's innocence.

Sullivan refused her request to force prosecutors to provide this extensive evidence last month, saying Flynn's lawyers "did not explain" how most of the information that had not yet been given to them was relevant to the crime he had committed.

"Flynn waived his right to trial when he pleaded guilty, and according to the cooperation agreement, he understood and agreed that it is the prosecutor who decides what the truthful statements are," said Joseph Tacopina, a leading criminal lawyer in New York, who was previously a prosecutor before the Brooklyn court.

"He's bound to it. But he's trying to turn it upside down and say that he's the one who determines what is true or not. That doesn't work if you sign a consent form," said Tacopina.