A federal judge on Sunday rejected former Trump adviser George PapadopoulosGeorge Demetrios PapadopoulosTale of two FBI cases: Clinton got warned, Trump got investigated Trump says he would consider pardons for those implicated in Mueller investigation New FBI document confirms the Trump campaign was investigated without justification MORE's effort to delay his prison term for lying to the FBI.

Politico reported that U.S. District Court Judge Randy Moss ruled Papadopoulos must report to prison on Monday after his argument to justify delaying his sentence failed. The judge cited Papadopoulos's decision not to appeal his sentence, and wrote that the defendant's challenge of special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's authority was unlikely to succeed.

Papadopoulos was sentenced to 14 days in prison in September after pleading guilty to lying to FBI agents about his contacts with Russia-linked individuals.

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Despite cooperating with Mueller’s investigation and expressing remorse at his sentencing, Papadopoulos went on to suggest publicly that his prosecution was a result of “entrapment" by western intelligence agencies. He said last month he was considering withdrawing from his plea agreement with the special counsel.

Mueller's team last week opposed Papadopoulos's effort to delay his prison sentence.

Papadopoulos argued that Mueller's appointment may be unconstitutional, citing a pending legal challenge by Roger Stone Roger Jason StoneThe agony of justice Our Constitution is under attack by Attorney General William Barr Justice IG investigating Stone sentencing: report MORE associate Andrew Miller.

The special counsel said, however, that Papadopoulos's claims were insufficient, writing in a court filing that they were made for "purposes of delay."

Moss on Sunday granted that request by the special counsel, saying that Papadopoulos missed his opportunity to challenge the constitutionality of Mueller's legality when he entered a guilty plea last year, according to Politico.

Moss also said that Miller's challenge against Mueller was unlikely to succeed, Politico added.

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"The court, accordingly, concluded that Papadopoulos has failed to carry his burden of demonstrating that the Court should continue his current bail status," Moss wrote, according to The Washington Post.

The former Trump campaign adviser, who Trump has described as a low-level staffer, is one of several previous associates of Trump who have either pleaded guilty or been indicted by Mueller in his investigation into Russian interference in the 2016 election.

--Michael Burke contributed to this report, which was updated at 12:10 p.m.