WASHINGTON — A federal judge who described himself as disgusted by Michael Flynn’s behaviour upended a straightforward sentencing hearing, postponing punishment for President Donald Trump’s first national security adviser and telling him in a stinging rebuke, “Arguably you sold your country out.”

Lawyers for Flynn requested the delay Tuesday after a tongue-lashing from U.S. District Judge Emmet Sullivan raised the prospect that Flynn could spend time behind bars for lying to the FBI about his Russian contacts.

Prosecutors hadn’t recommended prison, but the hearing that began with the defendant upbeat and smiling took an unexpected turn when the judge said his sentence would take into account not just Flynn’s extensive co-operation with investigators but also the lies the Trump administration official told from the grounds of the White House.

“I can’t make any guarantees, but I’m not hiding my disgust, my disdain for this criminal offence,” Sullivan said.

The postponement gave Flynn a chance to continue co-operating with the government in hopes of staving off prison and proving his value as a witness, including in a foreign-lobbying prosecution brought this week. The possibility of prison had seemed remote for Flynn since prosecutors had praised his co-operation, including 19 meetings with investigators.

But the judge’s upbraiding suggested otherwise and made clear that even defendants like Flynn who have co-operated in special counsel Robert Mueller’s Russia investigation may nonetheless be shadowed by the crimes that brought them into court in the first place. The hearing upset what had been a carefully crafted agreement and pushed months into the future a resolution of one of Mueller’s signature prosecutions.

“This is a very serious offence. A high-ranking senior official of the government making false statements to the Federal Bureau of Investigation while on the physical premises of the White House,” Sullivan said.

He later softened his tone, apologizing for suggesting that Flynn had worked as a foreign agent while in the White House when that other work had actually already ended. He also backpedaled on an earlier question on whether Flynn’s transgressions amounted to treason, saying he didn’t mean to suggest they did.

Flynn was to have been the first White House official sentenced in Mueller’s investigation into possible co-ordination between the Trump presidential campaign and Russia.

The hearing, though incomplete, marked a remarkable fall after a three-decade military career that included tours in Iraq and Afghanistan and oversight of the Defence Intelligence Agency during the Obama administration. Though Flynn served only briefly in Trump’s White House, he campaigned for him and attracted attention for leading a Republican National Convention crowd in a “Lock Her Up” chant about Hillary Clinton.

The hearing came amid escalating legal peril for Trump, who was implicated by federal prosecutors in New York this month in hush-money payments involving his former lawyer to cover up extramarital affairs. Nearly a half-dozen former aides and advisers have pleaded guilty, agreeing to co-operate with prosecutors. Some, like Flynn, were tripped up by concealing Russian contacts.

Flynn’s help in the probes was especially notable. Yet he’s nonetheless enjoyed Trump’s continued sympathy, thanks in part to a sentencing memo last week that tapped into the president’s suspicion of law enforcement and took aim at the FBI’s conduct during the investigation.

Trump tweeted “good luck” to Flynn hours before the sentencing and said that, “despite tremendous pressure being put on him,” there was “no Collusion!”

At the White House, press secretary Sarah Huckabee Sanders said Flynn’s actions had nothing to do with Trump. “It’s perfectly acceptable for the president to make a positive comment about somebody while we wait to see what the court’s determination is,” she said.

Sanders repeated her allegation that the FBI “ambushed” Flynn in an interview in which he lied. Of Trump’s earlier FBI criticism, she said, “We don’t have any reason to want to walk that back.”

Flynn’s legal woes stem from transition-period calls with then-Russian Ambassador Sergey Kislyak that raised intelligence community alarms even before Trump took office.

During those conversations, Flynn urged against a strong Russian response to Obama administration sanctions for Russian election interference and encouraged Russia’s opposition to a U.N. resolution on Israeli settlements. But when FBI agents approached him in the White House on Jan. 24, 2017, Flynn lied about those conversations, prosecutors said.

Flynn has never said why he lied, but Sullivan nonetheless castigated him for a deception that was then parroted by other senior administration officials.

The tone of Tuesday’s hearing startled Flynn supporters who hoped his lawyers’ arguments about the FBI’s conduct — they suggested he was discouraged from having a lawyer present during the interview and wasn’t informed it was a crime to lie — to resonate more than it did with Sullivan, who a decade ago tossed out the prosecution of a U.S. senator over government misconduct.

But while Sullivan tested those arguments, he was ultimately unmoved and Flynn mostly walked them back. He acknowledged that he indeed knew that lying to the FBI was a crime. Neither he nor his lawyers disputed that he’d lied to agents.

Flynn attorney Robert Kelner asked Sullivan not to penalize Flynn for the sentencing memo arguments, saying they were mostly intended to differentiate Flynn from other defendants in Mueller’s investigation who’d received prison sentences for lying. Though Sullivan said none of the other defendants was a White House official, Kelner suggested none had been as co-operative.

“He made the decision publicly and clearly and completely and utterly to co-operate with this investigation, knowing that because of his high rank, that was going to send a signal to every other potential co-operator and witness in this investigation,” he added.

After a prosecutor raised the prospect of Flynn’s continued co-operation with other investigations in the future, Sullivan warned Flynn that he might not get full credit for his assistance to the government if he were sentenced as scheduled.

Sullivan gave a visibly shaken Flynn a chance to discuss delaying the hearing with his lawyers. The court briefly recessed.

When they returned, Kelner requested a postponement so that Flynn could keep co-operating. Kelner said he expected Flynn would have to testify in a related trial in Virginia involving Flynn’s former business associates, and the defence wanted to “eke out the last modicum of co-operation” so he could get credit.

Flynn’s lawyers were instructed to submit a status report by March 13. ___

Read the Flynn FBI interview notes: http://apne.ws/xfm8IsO

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Associated Press writer Michelle R. Smith in Providence contributed to this report.

Eric Tucker And Chad Day, The Associated Press