(CNN) Robert Mueller's team of special prosecutors and the lawyers for George Papadopoulos delayed on Wednesday an upcoming check-in for the former Trump campaign staffer's case, an indication that the Mueller investigation will stay active until at least springtime and that Papadopoulos may continue to be useful to the prosecutors.

Papadopoulos pleaded guilty to lying to investigators in October, agreed to cooperate with Mueller's team and awaits receiving his sentence. Yet neither side has even suggested putting a date for Papadopoulos' sentencing on the calendar.

The lawyers in the case were scheduled to hold a phone call next Monday with the federal judge who will sentence Papadopoulos to discuss his status. But the two sides said in a court filing Wednesday they'd rather cancel it and discuss Papadopoulos' sentence three months from now. The deadline for the lawyers to update the court about Papadopoulos is April 23.

His defense attorney couldn't be reached Wednesday. Papadopoulos faces up to six months in prison and a fine of up to $9,500.

In another sign that Mueller's investigation isn't close to wrapping up, Michael Flynn, the former National Security Adviser who also pleaded guilty in December to lying to investigators in the Mueller probe, doesn't have a date for his sentencing, either.

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