Washington (CNN) Former national security adviser Michael Flynn, in a sworn affidavit on Wednesday, said he does not remember details of a phone call during the Trump presidential transition in 2016 to then-Russian Ambassador Sergey Kislyak about Russian policy and the United States' wishes.

"I still don't remember if I discussed sanctions on a phone call with Ambassador Kislyak nor do I remember if we discussed details of a UN vote on Israel," Flynn wrote. "The phone calls with Kislyak are still events of which I do not have a clear memory and it related to a general category of information (phone calls about foreign policy) that are both sensitive and classified."

The affidavit, an extraordinary move at this stage taken by a criminal defendant who's already admitted his guilt under oath twice, came among a bundle of court filings Wednesday that aim to back up Flynn's recent request to retract his guilty plea. In the hundreds of pages of their legal analysis, retelling of Flynn's plea discussions and exhibits, Flynn's legal defense team attempts to avoid his upcoming sentencing and convince the judge he was wronged by the Mueller investigation.

Flynn's new discussion of what happened is a revisionist take on one of the most significant episodes of 2016 -- a moment that contributed to a chain of events that's since defined the Trump presidency.

Previously, Flynn admitted to lying to the FBI and executive branch officials in the early days of the Trump administration about what was said in his calls with Kislyak. He resigned from the administration less than a month into the job, after officials privately expressed fears the Russians could exploit his lies. Flynn pleaded guilty to one criminal count of lying in December 2017, then became a pivotal witness in the Mueller investigation, especially regarding President Donald Trump's attempts to obstruct the Russia investigation that, at times, had centered on Flynn.

Read More