The office of US Special Counsel Robert Mueller (SCO) has recommended no jail time for Michael Flynn, President Donald Trump's former national security adviser, saying the retired general has provided "substanial assistance" to Mueller's investigation of Russian meddling in the 2016 US elections.

"The defendant assisted SCO's investigators on a range of issues, including interactions between individuals in the Presidential Transition Team and Russia," the SCO said in the court filing.

Flynn, a retired US army lieutenant general and former insider in Trump's circle, pleaded guilty in December to lying to the FBI about his contacts with the Russian ambassador to Washington.

Flynn was interviewed 19 times and assisted the Mueller team with investigating links between Russia and Trump's campaign and presidential transition team, the heavily redacted court filing said.

The filing comes as another Trump confidant, his personal lawyer Michael Cohen, reached a plea deal with the Mueller team last week.

Prosecutors said Flynn should be sentenced "at the low end of the guideline range—including a sentence that does not
impose a term of incarceration." 
His decision to plead guilty and cooperate likely influenced other witnesses' decision to cooperate with the Mueller probe, the SCO said.

Mueller's office added that Flynn "deserves credit for accepting responsibility in a timely fashion and substantially assisting the government." 

"The defendant's record of military and public service distinguish him from every other person who has been charged as part the SCO's investigation," the special counsel said.

Still the special counsel admonished Flynn saying his extensive government service "should have made him particularly aware" of the harm his actions caused.

Flynn was an early and avid supporter Trump's presidential campaign, and was named White House national security adviser shortly after the billionaire businessman's shock win.

The retired three-star Army general resigned in February 2017 after just 25 days in the position, admitting to having "inadvertently" given "incomplete information" to key people in the White House about his communication with the Russian ambassador.