COLLEGE PARK, MD. -- A Maryland man who is scheduled to plead guilty Tuesday in a case stemming from his alleged membership in a white supremacist group wants a federal judge to immediately sentence him at the hearing, a court filing shows.

William Bilbrough IV agreed to a specific term of imprisonment as part of his plea deal, a federal prosecutor said in a court filing Thursday. The filing does not specify a charge to which Bilbrough will plead guilty or the length of the prison term he would serve if U.S. District Judge Theodore Chuang accepts the plea agreement's terms.

FBI agents arrested Bilbrough and two other men in January as part of a broader investigation of a group called The Base. U.S. Army veteran Brian Mark Lemley Jr., of Elkton, Maryland, and Patrik Mathews, a former Canadian Armed Forces reservist, have pleaded not guilty to charges including transporting a firearm and ammunition with the intent to commit a felony.

Bilbrough was 19 and living with his grandmother in Denton, Maryland, at the time of his arrest. He was charged with conspiracy to transport and harbour Mathews, who is accused of illegally entering the U.S. from Canada.

Authorities said the three men were members of The Base and that the group's goal was to accelerate the overthrow of the U.S. government and replace it with a white supremacist regime. Authorities in Georgia and Wisconsin arrested four other men linked to The Base early this year.

Lemley and Mathews discussed "the planning of violence" at a gun rights rally in Richmond, Virginia, in January, according to prosecutors.

Bilbrough was not charged with any firearms-related offences. A prosecutor has said Bilbrough participated in early discussions about travelling to Richmond but had tried to distance himself from the group shortly before his arrest.

Lemley and Mathews also face separate but related federal charges in Delaware, where they shared a home. A closed-circuit television camera and microphone investigators installed in the home captured Lemley talking about using a thermal imaging scope affixed to his rifle to ambush unsuspecting civilians and police officers, prosecutors said.

"I need to claim my first victim," Lemley said last December, according to prosecutors.

Mathews talked about the Virginia rally as a "boundless" opportunity.

Mathews also videotaped himself advocating for killing people, poisoning water supplies and derailing trains, a prosecutor wrote in a court filing.

Defence attorneys have urged the judge to suppress all evidence captured by the surveillance equipment installed in the Delaware home.

"Such shocking incursions of personal privacy cannot be the penalty for exercising one's First Amendment right to free speech no matter how odious that speech may be," Mathews' attorney, Joseph Balter, wrote in an Aug. 31 court filing.

Prosecutors countered that the First Amendment "has nothing to do with this case."

"Speech and written words can prove intent and rationale behind criminal plans," they wrote.