A judge in the United States has delayed the sentencing of former National Security Adviser Michael Flynn for lying over Russian contacts to ensure he fully cooperates with an investigation into Moscow’s alleged role in President Donald Trump’s election campaign, ABC News reported.

Flynn had pleaded guilty in January 2017 for lying to the Federal Bureau of Investigation about his conversations with Russia’s then-ambassador to the US Sergey Kislyak in the weeks before Trump took office, CNBC reported. Flynn faced a standard sentence of zero to six months in prison.

Robert Mueller, who is looking into Russia’s alleged meddling in the 2016 United States elections, had proposed that Flynn receive no jail time for lying to the FBI.

Judge Emmet Sullivan said Flynn had behaved in a “traitorous” manner and gave him the option to move ahead with sentencing or put it off until Flynn can demonstrate his cooperation with the Russia collusion inquiry, AFP reported.

“I want to be frank with you, this crime is very serious,” Sullivan said. “I’m not hiding my disgust, my disdain. Arguably, you sold your country out.”

In a tweet before the sentencing was due, Trump had wished Flynn “good luck” and denied any collusion. “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,” the president had tweeted.