A United States judge is set to consider whether to impose the steepest sentence yet on two former leaders of the right-wing Proud Boys convicted of seditious conspiracy and other crimes for the January 6, 2021, assault on the Capitol by Donald Trump supporters.

Prosecutors are asking US District Judge Timothy Kelly to sentence Enrique Tarrio, the group’s former chairman, to 33 years in prison and to sentence his co-defendant Ethan Nordean, another former leader, to 27 years.

Those recommendations exceed the longest sentence handed out so far over the assault by the former president’s supporters on the seat of government, including Oath Keepers founder Stewart Rhodes who was sentenced in May to serve 18 years.

The attack was meant to stop Congress from certifying Democratic President Joe Biden’s election, which Mr Trump falsely claims was the result of widespread fraud.

Mr Trump currently holds a wide lead in the race for the Republican nomination to challenge Mr Biden in 2024.

Prosecutors are asking the judge to agree to a terrorism enhancement for Tarrio and his co-defendants – a move that has the potential to add roughly 15 years to a prison term.

“These defendants and the men in their command saw themselves as the foot soldiers of the right – they were prepared to use, and they did use, force to stop the ‘traitors’ from stealing the election’,” federal prosecutors wrote in their sentencing memo.

More than 1000 people have been arrested on charges related to the Capitol assault, and of those at least 570 have pleaded guilty and 78 have been convicted at trial.

Five people including a police officer died during or shortly after the riot and more than 140 police officers were injured.

The Capitol suffered millions of dollars in damage.

Special Counsel Jack Smith, who was tapped to investigate broader efforts to overturn the 2020 election, has since charged Mr Trump for trying to keep himself in power.

Lawyers for Tarrio and Nordean are asking the judge to reject the terrorism enhancement request.

“While the instant offences are serious in nature, they are nowhere near and should not be grouped in the same category … as the heinous acts committed by individuals such as Timothy James McVeigh,” Tarrio’s lawyers wrote, referring to the man who carried out the 1995 Oklahoma City bombing that killed 168 people.

In May, a jury convicted Tarrio and Nordean along with Joseph Biggs and Zachary Rehl of seditious conspiracy, a Civil War-era law that makes it a crime to conspire to oppose the government by force, and other felonies.

Biggs and Rehl are due to be sentenced on Thursday.

Prosecutors are seeking 33 years for Biggs and 30 years for Rehl.

A fifth defendant Dominic Pezzola was acquitted of the seditious conspiracy charge, but convicted alongside the others of other felonies including obstructing an official proceeding.

Prosecutors are requesting a 20-year sentence for him.

All of the five defendants except Tarrio entered the Capitol during the attack.

Prosecutors said they were among the first to charge past protective barricades.

Tarrio was not in Washington that day after being ordered by a judge to stay out of the city following a January 4 arrest for burning a Black Lives Matter banner at a church but prosecutors said he helped direct the attack from Baltimore.