Kevin Johnson and Bart Jansen | USA TODAY

AP

WASHINGTON – It all appeared to be a done deal.

Russia special counsel Robert Mueller urged that Michael Flynn, President Donald Trump's former national security adviser, serve no prison time for his communication with Russian Ambassador Sergey Kislyak.

Flynn stepped to the lectern in federal court Tuesday to declare he was ready to accept responsibility for his crimes and proceed to sentencing.

Nobody in the packed courtroom – especially Flynn – expected the blistering rebuke unleashed by U.S. District Judge Emmet Sullivan, who went as far as to question the patriotism of the retired three-star Army general, wheeling to face the courtroom’s American flag to suggest that Flynn’s conduct “undermined” all the banner stood for.

“Arguably, you sold your country out,” Sullivan said.

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Former national security adviser Michael Flynn arrives for sentencing hearing

At the end of the extraordinary hearing, Flynn’s attorneys acceded to Sullivan’s warning that they postpone sentencing at least until March. The move allows Flynn to formally complete his cooperation with Mueller’s team in the Russia investigation and at least one other inquiry in which two of Flynn’s former business associates were charged this week with illegal lobbying on behalf of the government of Turkey.

Rarely are cooperating witnesses sentenced before their assistance is completed, Sullivan told Flynn, expressing "disgust" over Flynn's conduct.

Last week, attorneys raised the notion that Flynn might have been entrapped during an FBI interview Jan. 24, 2017, when the national security adviser falsely denied discussing newly imposed Russian sanctions with Kislyak.

Almost immediately after Tuesday's hearing opened, Sullivan seized on the claims made by Flynn's lawyers, who suggested that agents had not properly warned their client of the criminal consequences for lying to the FBI.

Sullivan asked whether Flynn asserted the claims in an effort to cast doubt on his guilty plea.

Defense attorney Robert Kelner disavowed any such attempt, asserting that "Gen. Flynn fully accepts responsibility."

The tenor of the hearing – and the judge – suddenly turned against the decorated military officer and vocal Trump surrogate.

Asked whether he needed more time to consider the claims related to the FBI interview, Flynn told the judge, "I appreciate that. No. I would like to proceed, your honor."

The expectation that Tuesday's hearing would allow Flynn and his family to finally turn the page on an exacting yearlong slog through the most high-profile criminal investigation in the country all but drained away as Sullivan recounted Flynn's false statements as a ranking official in Trump's White House.

"I'm going to be frank with you," Sullivan said. "This is a very serious offense. It involves making false statements to the FBI on the premises of the White House – in the West Wing!"

The interview with FBI agents occurred in Flynn's White House office, four days after he assumed his post as national security adviser.

George Frey, George Frey

Though Sullivan referenced Flynn's career military service and lack of a prior criminal record, he suggested that Flynn's conduct marked a serious betrayal he could not ignore.

"I cannot hide my disgust or my disdain for the crimes you committed," Sullivan said.

The judge drew a head-snapping response from the defense table when he asked prosecutors whether Flynn's behavior amounted to "treason."

Prosecutors said there was no basis for such a charge, and the judge walked back the reference, saying he did not mean to imply Flynn committed treason.

"Don't read too much into my questions," Sullivan told the courtroom gallery after returning from a short break.

The judge's admonition could not erase the sting inflicted on the combat veteran and career military officer.

"I cannot assure you that, if you proceed today, you will not be sentenced to a period of incarceration," Sullivan told Flynn, suggesting that he seek a delay until his cooperation was complete so it could count in his favor.

After a short recess to confer, Kelner said Flynn would seek the postponement, asserting that his client "held nothing back” from prosecutors.

Kelner said Flynn would probably be called to testify at any trials of two former business associates accused of illegal lobbying on behalf of the Turkish government.

The charges were unveiled Monday, and prosecutors acknowledged that Flynn could have faced charges in that case had he not agreed to cooperate with Mueller's team.

As part of his plea, Flynn admitted lying about his Turkish lobbying efforts. He belatedly registered with the Justice Department as a foreign agent for Turkey.

"I’m not promising anything,” Sullivan told Kelner about sentencing. “The court was just being upfront with you.”

Sullivan set a status conference in the case for March, but before adjourning the session, he offered one last parting shot:

"Happy holidays," he said.

Flynn, accompanied by his wife, left the courthouse, rushing through a gantlet of protesters and supporters to a waiting car without comment.

"Lock him up!" some called out, echoing Flynn's similar refrain at the podium of the 2016 Republican Convention, when he referred to Democratic nominee Hillary Clinton and the email investigation that shadowed her campaign.

Other placard-waving demonstrators shouted encouragement to Flynn, chanting, "USA! USA!"