The House committee investigating the 2021 assault on the US Capitol by supporters of Donald Trump will examine links between associates of the former president and right-wing extremist groups at its seventh hearing on Tuesday.

"We'll give the American public a more complete understanding of the final phase of president Trump and his supporters' use of radical measures to prevent the peaceful transfer of power and overturn the 2020 election," a committee aide said.

The session will focus on ties between members of Trump's inner circle and two militia groups, the Proud Boys and the Oath Keepers, the aide said.

"We are going to be connecting the dots during these hearings between these groups and those who were trying -- in government circles -- to overturn the election," Democratic Representative Zoe Lofgren of California said.

Members of the Proud Boys and Oath Keepers stormed Congress on January 6, 2021 along with thousands of Trump loyalists in an attempt to prevent the certification of Democrat Joe Biden's election victory.

Jason Van Tatenhove, a former member of the Oath Keepers, is expected to testify at Tuesday's televised hearing, which begins at 1:00 pm (1700 GMT) and is expected to last at least two hours.

Stephen Ayres, an Ohio man who drove to Washington and joined the mob which stormed the Capitol, is also expected to appear as a witness.

Five members of the Proud Boys were indicted in June on seditious conspiracy charges and 11 members of the Oath Keepers face the same charges. Three of the Oath Keepers have pleaded guilty.

More than 850 people have been arrested in connection with the storming of Congress by Trump supporters, but only those 16 face seditious conspiracy charges, which carry a sentence of up to 20 years in prison.

The committee is trying to determine whether Trump or his associates had a role in planning or encouraging the violent insurrection and has subpoenaed numerous advisors and aides to the former president.

Excerpts may be played on Tuesday from an eight-hour interview the committee held Friday with former Trump White House counsel Pat Cipollone.

'Pivotal moment'

The assault on the Capitol left at least five people dead and 140 police officers injured, and followed a fiery speech by Trump to thousands of his supporters near the White House.

Trump was impeached for a historic second time by the House of Representatives after the riot -- he was charged with inciting an insurrection -- but was acquitted by the Senate.

In a statement Tuesday on the Truth Social platform, Trump denounced the committee as "Political Hacks and Thugs."

"Have you seen them before?" he asked. "Yes, they are essentially the same lunatics that drove the Country 'crazy' with their lies and made up stories, like RUSSIA, RUSSIA, RUSSIA, and all of the others."

Tuesday's hearing will be the first since blockbuster testimony by Cassidy Hutchinson, an assistant to Trump's chief of staff Mark Meadows.

Hutchinson testified late last month that she was told Trump had angrily lunged at his Secret Service driver and grabbed at the steering wheel of his limousine in a bid to join the crowd marching on Congress.

The select committee aide said Tuesday's hearing will focus on a tweet Trump sent in December telling his supporters to come to Washington on January 6 and promising it will be "wild."

"They immediately started answering his call by zeroing in on that date," the aide said. "We'll talk about how that was a pivotal moment that spurred a chain of events."

The tweet was sent a little more than an hour after Trump met at the White House with his lawyer Rudy Giuliani, former general Mike Flynn, and Sidney Powell, another attorney, the aide said.

The hearing will also look at attempts by some Republican members of Congress to pressure vice president Mike Pence into blocking certification of the election results.