WASHINGTON – Citing the "substantial" assistance provided by former national security adviser Michael Flynn, Justice Department special counsel Robert Mueller is recommending no prison time for the retired Army lieutenant general who had pleaded guilty last year to making false statements to federal investigators.

"Given the defendant’s substantial assistance and other considerations set forth below, a sentence at the low end of the guideline range—including a sentence that does not impose a term of incarceration—is appropriate and warranted," Mueller's team said in a heavily-redacted memorandum prepared in advance of Flynn's sentencing later this month.

The court documents indicated that Flynn had met with investigators 19 times during the past year in which he has been cooperating with Mueller's team on multiple investigations, including the special counsel's inquiry into possible coordination between the Trump campaign and Russia.

References to other investigations were redacted from the court documents, along with details about how Flynn's cooperation had contributed to the probes. Nevertheless, prosecutors were effusive in their praise of Flynn's early and wide-ranging cooperation.

“The defendant’s decision to plead guilty and cooperate likely affected the decisions of related firsthand witnesses to be forthcoming with the (special counsel’s office) and cooperate,” Mueller's team said in Tuesday's late evening court filing.

More:Read Mueller memo on Michael Flynn's cooperation in the Russia investigation

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In recommending the lightest possible sentence, prosecutors noted Flynn's past exemplary service.

"The defendant’s record of military and public service distinguish him from every other person who has been charged as part the (special counsel's) investigation," prosecutors said. "However, senior government leaders should be held to the highest standards. The defendant’s extensive government service should have made him particularly aware of the harm caused by providing false information to the government, as well as the rules governing work performed on behalf of a foreign government."

Flynn's son, Michael Flynn Jr., thanked those who had supported his family.

"God is good," the son tweeted late Tuesday. "To those who have supported us throughout this process.... Thank you from the bottom of my heart. I will never forget you."

The memo is the first in a series of developments expected over the coming weeks in Mueller's ongoing investigation into Russian interference in the 2016 election.

On Friday, Mueller’s team will explain its reasons for abandoning a plea agreement with Paul Manafort, former campaign chairman for President Donald Trump. And Michael Cohen, Trump’s former personal lawyer, will be sentenced Dec. 12 for lying to Congress about a Trump Organization real estate deal in Moscow.

Trump has repeatedly criticized the probe as a “witch hunt” and has denied any cooperation between his campaign and Russia.

Flynn, who memorably called for the jailing of Democrat Hillary Clinton during the 2016 Republican convention, pleaded guilty Dec. 1, 2017, to lying to the FBI about his contacts with Russia during the presidential transition. U.S. District Judge Emmet Sullivan will sentence Flynn Dec. 18.

Flynn admitted to lying during an FBI interview about his conversations with Sergey Kislyak, Russia’s ambassador to the United States. Flynn discussed U.S. sanctions with Kislyak on Trump’s behalf during the presidential transition and said members of the president’s inner circle were aware of, and in some cases directing, his efforts, according to the plea.

Flynn had urged Kislyak not to respond to sanctions imposed by the Obama administration in response to Russian election interference.

Flynn’s FBI interview occurred in January 2017, shortly after he took his post as national security adviser in the Trump White House. He was forced to resign in February 2017. The White House said he was fired for misleading Vice President Mike Pence and other senior officials about the content of his conversations with Kislyak.

As part of his plea, Flynn also admitted to lying about Turkish lobbying and research work. He belatedly registered with the Justice Department as a foreign agent for the work weeks after he left the White House.

Other revelations are expected to follow in the Mueller investigation. In Manafort's case, prosecutors abandoned a plea deal by arguing that he repeatedly lied to investigators after agreeing to cooperate.

But the filing Nov. 26 didn’t detail the lies, so another filing scheduled Friday will be the first explanation from prosecutors about what happened.

Manafort’s lawyers have denied he breached the agreement. They will get a chance to respond to what prosecutors say before U.S. District Judge Amy Berman Jackson sentences him March 5.

Manafort pleaded guilty in September in her court to conspiracy and obstruction of justice for representing a pro-Russia faction in Ukraine. A federal jury in Virginia also found him guilty in August on banking and tax charges. U.S. District Judge T.S. Ellis will sentence him Feb. 8 in that case.

Trump caused a stir after the plea deal fell apart by suggesting he could still pardon Manafort, who has a joint defense agreement with the president.

“It was never discussed, but I wouldn’t take it off the table," he told the New York Post in an Oval Office interview. "Why would I take it off the table?"

Cohen’s case dealt with preliminary planning for a Trump Tower in Moscow, which continued during the 2016 presidential campaign for months longer than Trump, presidential campaign officials and others acknowledged at the time.

Cohen asked U.S. District Judge William Pauley in New York on Friday to spare him prison time after pleading guilty Thursday to lying to Congress.

Cohen has been cooperating with Mueller’s team since August. He has also pleaded guilty to federal charges related to hush payments he made to two women who said they had extramarital affairs with Trump.

Trump said after the plea that Cohen was weak.