Michael Flynn pleaded guilty in December 2017 to lying to FBI agents about his conversations with Sergei Kislyak, Russia's ambassador in Washington at the time.
The sentencing of Michael Flynn, President Donald Trump's former US national security advisor, has been postponed to March 13 next year.
Flynn appeared before US District Judge Emmet Sullivan on Tuesday for his sentencing, but his attorneys requested a postponement to allow him to continue cooperating with an FBI investigation.
Flynn pleaded guilty in December 2017 to lying to FBI agents about his conversations with Sergei Kislyak, Russia's ambassador in Washington at the time, in a case that grew out of a federal investigation into possible collusion between US President Donald Trump's campaign and Russia in the 2016 US presidential election.
"I'm not hiding my disgust, my disdain for this criminal offence," Judge Sullivan said, noting that Flynn had lied to White House officials, who in turn lied to the public.
"Arguably that undermines everything that flag over there stands for," he said, referring to the American flag. "Arguably you sold your country out."
In court for his sentencing, Flynn stood by his guilty plea.
TRT World's Nicole Johnston reports.
Large inflatable rat
In an earlier filing with the court, a lawyer for Flynn had noted that he was not warned during an FBI interview that lying would be a crime.
But an attorney for Flynn told the court during the sentencing hearing that Flynn was not entrapped.
Hours before the hearing, Trump appeared to offer support for his former campaign adviser and White House aide. Several protesters were at the courthouse as Flynn arrived, along with a large inflatable rat.
"Good luck today in court to General Michael Flynn. Will be interesting to see what he has to say, despite tremendous pressure being put on him, about Russian Collusion in our great and, obviously, highly successful political campaign. There was no Collusion!" Trump wrote on Twitter.
Good luck today in court to General Michael Flynn. Will be interesting to see what he has to say, despite tremendous pressure being put on him, about Russian Collusion in our great and, obviously, highly successful political campaign. There was no Collusion!— Donald J. Trump (@realDonaldTrump) December 18, 2018
Mueller... Robert Mueller
Special Prosecutor Robert Mueller, leading the investigation into Russian interference in the 2016 election and whether Trump has unlawfully sought to obstruct the probe, has asked Sullivan not to imprison Flynn because of his military service and his "substantial" cooperation with the probe.
Flynn told investigators in January 2017 that he had not discussed US sanctions against Russia with Kislyak, when in fact he had, according to his plea agreement.
Lying to the FBI carries a statutory maximum sentence of five years in prison.
Flynn's plea agreement states that he is eligible for a sentence of between zero and six months and can ask the court not to impose a fine.
Flynn's lawyers have asked the court for a probation term of no more than one year, with minimal conditions of supervision, and 200 hours of community service.
They said he deserved leniency because he was not warned before the meeting with FBI agents that it was a crime to lie to the agents.
They also said that then-FBI Deputy Director Andrew McCabe had told Flynn the "quickest way" to conduct the interview was without counsel present.
Critics of the Mueller probe argue that Flynn, who held the White House job for only 24 days, was set up.
"He was certainly ambushed," White House spokeswoman Sarah Sanders told Fox News in an interview ahead of the hearing, referring to Flynn. Sanders also alleged that the FBI had a "clear political bias" against Trump, although in June a Justice Department inspector general report found no evidence of bias at the top US law enforcement agency.
Mueller countered in a court filing last week that Flynn had no cause to lie in the interviews and that a "sitting National Security Advisor, former head of an intelligence agency, retired Lieutenant General, and 33-year veteran of the armed forces knows he should not lie to federal agents."
On Monday, Sullivan ordered the special counsel to release a redacted, five-page FBI account of Flynn's January 2017 interview, saying it was relevant to his sentencing. Mueller's team later filed their 10-page memo detailing Flynn's responses to investigators.
Mueller's wide-ranging probe has so far ensnared 32 individuals and three Russian firms. Trump has said he fired Flynn in early 2017 for lying to Vice President Mike Pence over his contacts with Russians, but that Flynn's actions were lawful.
Trump has denied any collusion with Moscow and has labelled Mueller's investigation a "witch hunt." Russia denies it meddled in the election, contrary to the conclusion of US intelligence agencies.