"Due to the status of its investigation, the Special Counsel's Office does not believe that this matter is ready to be scheduled for a sentencing hearing at this time," read a joint status report released Tuesday.

Tuesday's delay is the fourth time prosecutors have asked to delay Flynn's sentencing.

Both parties will now be required to submit status reports by Sept. 17. Mueller had previously asked for status reports by Aug. 24, when he delayed scheduling the sentencing at the end of June.

Flynn pleaded guilty to lying to the FBI during their investigation of Russian interference in the 2016 election in December. Prosecutors say Flynn lied to FBI investigators about his contact with then-Russian Ambassador Sergey Kislyak.