(Photo: CGTN)

Special Counsel Robert Mueller recommended in a court filing on Friday that a judge sentence former Trump campaign aide George Papadopoulos to up to six months in prison for lying to federal agents investigating whether Russia interfered in the 2016 US presidential election.

Papadopoulos pleaded guilty in October to lying to FBI agents and is scheduled to be sentenced on Sept. 7.

According to Special Counsel Robert Mueller's sentencing memorandum to the judge, Papadopoulos lied about his contacts with people who claimed to have ties to top Russian officials, including his meeting with a professor who said Russia had "dirt" on Democratic presidential candidate Hillary Clinton.

"The defendant's crime was serious and caused damage to the government's investigation into Russian interference in the 2016 presidential election," Mueller's memo said.

"The defendant lied in order to conceal his contacts with Russians and Russian intermediaries during the campaign and made his false statements to investigators on January 27, 2017, early in the investigation, when key investigative decisions, including who to interview and when, were being made," Mueller said.

Mueller said the government believed a sentence of up to six months in prison was "appropriate and warranted" along with a fine of $9,500.

Muller also indicated that Papadopoulos had not fully cooperated with prosecutors.

"The defendant did not provide 'substantial assistance,' and much of the information provided ... came only after the government confronted him with his own emails, text messages, Internet search history and other information it obtained via search warrants and subpoenas," Mueller wrote.