A federal judge agreed Tuesday to postpone Michael Flynn’s sentencing after a hearing to decide the punishment for President Donald Trump’s former national security adviser went awry.

The surprise development came after Judge Emmet Sullivan in Washington, D.C., offered to give Flynn, a retired lieutenant general, more time to consider his decision to plead guilty to lying to investigators probing Russia’s interference in the 2016 election. Sullivan described the offense as “serious” and said he could not guarantee a sentence without prison time, even after the special counsel’s office recommended that Flynn not be incarcerated.