A US judge has delayed sentencing of former national security adviser Michael Flynn to ensure he cooperates fully with an investigation into possible collusion between Donald Trump's 2016 campaign and Russia.
During the sentencing hearing, US District Judge Emmet Sullivan told the retired lieutenant general that he had "arguably" sold out his country in lying to the FBI.
Flynn pleaded guilty in December 2017 to lying to FBI agents about his conversations with Sergei Kislyak, Russia ambassador in Washington at the time.
Special Counsel Robert Mueller, leading the Russia investigation, had asked the judge not to sentence Flynn to prison because he already had provided "substantial" cooperation to prosecutors over the course of many interviews.
But the judge told Flynn his behaviour was abhorrent, noting that the former national security adviser had also lied to White House officials, who in turn lied to the public.
"Arguably, you sold your country out," Judge Sullivan said. "I'm not hiding my disgust, my disdain for this criminal offence."
The judge also noted that Flynn was operating as an undeclared lobbyist for Turkey even as he worked on Trump's election team and prepared to be his national security adviser.
At one point, the judge asked prosecutors if Flynn could have been charged with treason, although he later said he had not been suggesting such a charge.
Judge Sullivan appeared ready to sentence Flynn to prison but then gave him the option of a delay in his sentencing so that he could fully cooperate with any pending investigations. Flynn accepted that offer.
Prosecutors said Flynn had already provided most of the cooperation that he could, but it was possible he might be able to help investigators further.
The judge did not set a new date for sentencing but asked for a status report by 13 March.
In a separate development on Tuesday, Bijan Rafiekian, Flynn's former business partner, pleaded not guilty in federal court in Alexandria, Virginia, after being charged by US prosecutors with unregistered lobbying for Turkey.
Prosecutors say the lobbying effort was aimed at having the United States extradite a Muslim cleric who lives in the United States and is accused by Turkey's government of backing a 2016 coup attempt. Flynn is expected to testify in the trial, scheduled to start on 11 February.
Flynn served as a high-profile adviser to Trump's election campaign team, and at the Republican Party's national convention in 2016 he led Trump's supporters in cries of "Lock her up!" directed against Democratic candidate Hillary Clinton. He became national security adviser when Trump took office in January 2017 but lasted only 24 days before being ousted.
Several protesters were at the courthouse on Tuesday as Flynn arrived, along with a large inflatable rat.
Lying to the FBI carries a statutory maximum sentence of five years in prison. Flynn's plea agreement stated that he was eligible for a sentence of between zero and six months.