U.S. prosecutors and attorneys for Michael T. Flynn asked a federal judge Friday to begin the process of preparing to sentence President Trump’s former national security adviser but said it still was premature to seek a sentencing date in special counsel Robert S. Mueller III’s ongoing investigation.

Flynn pleaded guilty in December to lying to the FBI about contacts with then-Russian Ambassador Sergey Kislyak, becoming one of the first Trump associates to cooperate and the highest-ranking official charged in Mueller’s ongoing probe of Russian interference in the 2016 presidential election.

“Due to the status of the special counsel’s investigation, the parties do not believe that this matter is ready to be scheduled for a sentencing hearing at this time,” prosecutor Brandon L. Van Grack and Flynn attorney Robert K. Kelner wrote.

They asked to update the court August 24.

Mueller’s office for months has sought to question the president about events that led to his decisions to oust Flynn and FBI director James B. Comey, including scrutinizing possible efforts by the president or others to impede the special counsel’s probe, The Washington Post has reported.

In a joint court filing Friday, neither party gave any sign of the state of talks with the president’s lawyers but asked the judge to refer Flynn’s case to U.S. probation officials to prepare a pre-sentencing report — the first step to bringing his case to a close.

The pre-sentencing report is an investigation into whether a person’s background may warrant a harsher or more lenient sentence, takes 70 to 90 days to prepare and is a necessary step in the federal system before sentencing. However, prosecutors are not required to set a sentencing date even after the report is complete.

The Flynn filing came one day after Mueller’s office and two other cooperating defendants charged last year advanced toward sentencing. A judge Thursday set a Sept. 7 hearing for George Papadopoulos, a former Trump campaign adviser who pleaded guilty in October to lying to the FBI about his Russian contacts.

The special counsel’s office and defense attorneys also requested sentencing Sept. 17 for Richard Pinedo, a California man whose guilty plea was announced in February in connection with a Russian Internet trolling operation whose alleged members were charged in a broader indictment.

Flynn resigned from his top White House post in February 2017 after the White House said that he misled Vice President Pence and other administration officials about his contacts with Kislyak.

Flynn’s plea revealed that he was in touch with senior Trump transition officials before and after his communications with the ambassador. The pre-inauguration communications with Kislyak involved efforts to blunt Obama administration policy decisions — on sanctions on Russia and a United Nations resolution on Israel — potential violations of a rarely enforced law.

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