President Donald Trump’s former deputy campaign chairman Rick Gates has been sentenced to 45 days in jail and three years of probation after he pleaded guilty to conspiracy and lying in the investigation into Russian interference in the 2016 US election.

US District Judge Amy Berman Jackson said that while she was moved by his extensive co-operation with prosecutors, she still felt some punishment was in order.

She said she had struggled for some time with how to sentence Gates, who met with investigators more than 50 times and helped the government secure convictions of Republican operatives Paul Manafort and Roger Stone after he pleaded guilty in February 2018 to lying to the FBI and the special counsel’s office and conspiring against the United States.

Ms Jackson said that every day she sees people who commit crimes “of a much more limited scope” than Gates’ offences who are motivated by drug addictions and poverty and who then, like Gates, become government witnesses by turning on their own friends and neighbours.

“Even they often serve some time,” Ms Jackson noted.

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Gates, who held senior posts on the president’s campaign team and inauguration committee, was one of several former Trump aides and advisers to be charged in Mueller’s investigation that documented Russian interference in the 2016 US election.

Gates, 47, initially pleaded not guilty but reversed himself in February 2018 and agreed to co-operate with prosecutors.

Former Trump campaign aide Rick Gates leaves federal court after sentencing. Photo: Getty

Ms Jackson also said he will be required to pay a $US20,000 ($A29,000) fine, complete community service and continue co-operating in several ongoing investigations.

“I wish to express to this court that I accept complete responsibility for my actions that have led me here,” Gates said before he was sentenced on Tuesday.

“I greatly regret the mistakes I have made and I have worked hard to honour my commitment to make amends. My family and I appreciate your consideration for leniency, and I hope and pray that you will give that to me.”

Under the sentencing guidelines calculated by the government, he could have faced up to almost five years in prison.

-AAP