Former U.S. National Security Adviser Michael Flynn departs U.S. District Court, where he was expected to plead guilty to lying to the FBI about his contacts with Russia's ambassador to the United States, in Washington, U.S., December 1, 2017.

The criminal sentencing of President Donald Trump's first national security advisor Michael Flynn will be on hold for at least another two months, a federal judge said Monday during a status conference hearing in U.S. District Court in Washington, D.C.

Judge Emmet Sullivan told Flynn's new lawyer and prosecutors that they should let him know by Aug. 31 whether they are ready for Flynn to be sentenced for his admitted crime of lying to the FBI about the nature of his discussions with Russia's then-ambassador to the United States, Sergey Kislyak, in the weeks before Trump's inauguration.

Sullivan told the parties to file their next status report by that date. Flynn's new lawyer, Sidney Powell, had wanted three months to get up to speed in the case by reviewing what she called a "massive" amount of material turned over by prosecutors.

In the meantime, the retired Army lieutentant general Flynn, who had pleaded guilty in December 2017 to a charge lodged by then-special counsel Robert Mueller, is expected to be called as a witness at the upcoming trial of two former business associates.

Flynn's appearance Monday in Sullivan's courtroom was his first since an aborted sentencing hearing last December, and the first with Powell, whom he hired after firing his previous lawyers.

Powell, a pro-Trump lawyer who previously had criticized the case against Flynn, said his cooperation with prosecutors as part of a plea deal is "ongoing."

Flynn originally was due to be sentenced by Sullivan in December 2018.

At that sentencing hearing, the judge verbally tore into Flynn, saying, "Arguably, you sold your country out."