Former White House National Security Advisor Michael Flynn leaves the Prettyman Federal Courthouse following a sentencing hearing in U.S. District Court December 18, 2018 in Washington, DC.

President Donald Trump's former national security advisor Michael Flynn has completed his cooperation with Robert Mueller's investigation, said the special counsel's office.

That development, outlined in a joint status report filed Tuesday by attorneys for Flynn and Mueller, follows a dramatic December sentencing hearing in which Judge Emmet Sullivan told Flynn "you sold your country out."

Sullivan at the time postponed sentencing until Flynn could finish cooperating with the government and suggested that could result in a lighter sentence.

"The court likes to be in a position to say there is nothing else this defendant can do to help the United States of America," Sullivan said.

Despite the special counsel's view that Flynn has completed his cooperation, Flynn remains "in a position to cooperate with law enforcement authorities," according to the status report.

Flynn may continue to cooperate with prosecutors in Virginia who are investigating his former business partners, Bijan Rafiekian and Kamil Alptekin, ahead of a trial slated to begin in July. The two men have denied charges that they unlawfully lobbied on behalf of Turkey.

But the attorneys wrote that "in the government's view his cooperation is otherwise complete."

Flynn is likely to face a sentence of between zero and six months in jail, according to federal guidelines. Mueller's office has recommended that he receive the low end of that range. Flynn pleaded guilty in 2017 to lying to federal investigators about conversations he had with the Russian ambassador.

On Wednesday, Trump's former campaign chairman Paul Manafort was sentenced to 43 months of prison time on conspiracy charges, bringing his total sentence on charges brought by the special counsel to more than seven years.

— CNBC's Kevin Breuninger contributed to this report.