George Papadopoulos, the former Trump adviser who claims Alexander Downer and the Australian government spied on him before the 2016 US presidential election, has asked a judge to delay the start of his prison sentence.
Papadopoulos was sentenced to 14 days' prison after pleading guilty in September in the US District Court in Washington DC to lying to the FBI.
He is scheduled to start the prison sentence on November 26.
The 31-year-old from Chicago was prosecuted by US Special Counsel Bob Mueller, but Papadopoulos' lawyers argue he should not go behind bars until separate court proceedings challenging the constitutionality of Mueller's appointment are decided.
"If the appeal is successful, then the Special Counsel lacked constitutional authority to prosecute Mr Papadopoulos in the first instance," Papadopoulos' lawyers wrote in Friday's court filing.
Papadopoulos risks "unnecessarily serving a sentence of incarceration that was unconstitutionally obtained" and suffering "irreparable harm", his lawyers added.
Prosecutors are yet to respond.
Papadopoulos met with then Australian high commissioner to the UK Downer at a London wine bar in May 2016, six months before Donald Trump's presidential election win over Hillary Clinton.
At this meeting Downer claimed Papadopoulos said, "the Russians might use material that they have on Hillary Clinton in the lead-up to the election, which may be damaging".
Mr Downer told the The Australian newspaper in an interview that he had reported the information to Canberra.
This information has been described as the starting point that led to an FBI investigation and then the Mueller probe into Russia's efforts to interfere with the 2016 election.
Papadopoulos said in media interviews he could not recall telling Downer about the Russian dirt information, but admitted raising it with Greece's foreign minister in another meeting.
He has accused Downer and the Australian and UK governments of spying on him.
Downer has rejected the claim.
Papadopoulos admitted in the US District Court proceedings to lying to the FBI about his contact with Russian nationals and Maltese professor Joseph Mifsud, and an attempt to arrange a meeting in 2016 between Trump and Russian President Vladimir Putin.