Prosecutors working for special counsel Robert S. Mueller III asked a federal judge Wednesday to order George Papadopoulos, a former campaign adviser to President Trump, to start serving time in prison on Monday as scheduled.

Papadopoulos’s lawyers had asked U.S. District Court Judge Randolph D. Moss to allow Papadopoulos to delay his two-week prison sentence while a constitutional challenge to Mueller’s appointment filed in a separate case in Washington is resolved.

But Mueller’s team responded that Papadopoulos waived his rights to appeal when he pleaded guilty to lying to the FBI and that he had failed to file his request in a timely fashion.

In the more than a year since Papadapoulos was first charged by Mueller’s office, he has never challenged the constitutionality of the special counsel’s appointment. Papadopoulos’s motion citing the D.C. case was made just days before the scheduled start to his brief prison stay.

An appeals court in Washington heard oral arguments earlier this month in the constitutional challenge, which was made by a former aide to Trump adviser Roger Stone who is fighting a subpoena to appear before the grand jury. It is not clear when the three-judge panel is likely to rule in the case, which may ultimately go to the Supreme Court.

Mueller’s prosecutors said Papa­dopoulos’s own public statements since he was sentenced suggested that his filing was solely an effort to delay his incarceration.

Chris LaVigne, an attorney for Papadopoulos who recently replaced the lawyers who represented him during the plea process, said in a statement that the special counsel’s motion had failed to address the central question of Papadopoulos’s request: “Why should Mr. Papadopoulos be required to begin serving his sentence now, when there is an appeal pending that could directly impact the validity of his prosecution and conviction?”

Prosecutors had asked Moss to sentence Papadopoulos to as much as six months in prison for lying to federal agents about key details involving his interactions with a London-based professor and two Russian nationals.

But at his sentencing hearing, Papadopoulos appealed for mercy, saying that he understood his lies had been wrong and that he was remorseful.

Moss told Papadopoulos that he had been planning to order him to serve 30 days, but shaved the sentence to 14 days because he was moved by his contrition.

Following the hearing, Papadopoulos gave a series of interviews in which he expressed views that the special counsel’s office described Wednesday as “inconsistent with his stated acceptance of responsibility at sentencing.”

For instance, he told Fox News days later that he was considering withdrawing his plea and that he should not “have to serve even one day in jail for something that now it seems was completely orchestrated.”

He also tweeted on Nov. 9 that his biggest regret was pleading guilty.

“The defendant received what he bargained for, and holding him to it is not a hardship,” prosecutors wrote Wednesday.

LaVigne called the special counsel’s inclusion of Papadopoulos’ public remarks “unrelated and wholly irrelevant” to the legal motion.

Papadopoulos’s prison term would mark an important milestone for the investigation, which began when an Australian diplomat alerted U.S. officials in July 2016 that Papadopoulos had claimed to have been told the Russians held dirt about Democratic presidential candidate Hillary Clinton in the form of thousands of emails.