Donald Trump has revealed he is considering a "full pardon" for Michael Flynn, his first national security adviser.

Flynn admitted making false statements to the FBI about his dealings with the Russian ambassador to US before Trump's inauguration, but he sought to withdraw the guilty plea in January, arguing that prosecutors violated his rights and duped him into a plea agreement.

In a tweet on Sunday, the president said: “So now it is reported that, after destroying his life & the life of his wonderful family (and many others also), the FBI, working in conjunction with the Justice Department, has ‘lost’ the records of General Michael Flynn. How convenient.”

He added: “I am strongly considering a Full Pardon!”

The president’s allegations about the FBI and Department of Justice collaborating to lose “records” are non-specific and unsubstantiated at this time.

Flynn was supposed to cooperate with the government as part of his plea deal. But he later switched lawyers and tactics, arguing that prosecutors in the case had violated his rights and tricked him into lying about his December 2016 conversations with Sergei Kislyak, then Moscow's ambassador in Washington.

The Department of Justice has repeatedly denied allegations of prosecutorial misconduct.

US District Court Judge Emmet Sullivan rejected all of Flynn’s claims in December and set a sentencing date.

Shortly after that, Flynn filed the motion to withdraw his plea.

Flynn, who also previously led the Defence Intelligence Agency, served just 24 days in the Trump administration before he was fired in January 2017.