Keller faces a maximum sentence of 20 years in prison for obstructing an official proceeding, but the Los Angeles Times reports he is now cooperating with investigators, indicating a far more lenient punishment is likely.

The first Capitol rioter to be sentenced - Paul Allard Hodgkins - was jailed for eight months after admitting the same offence as Keller.

Keller admitted to destroying a phone and memory card which contained images of him inside the Capitol, as well as discarding the Team USA jacket he wore at the insurrection, in court documents.

A sentencing date has not yet been set.

Keller had been indicted on seven counts, but admitted one as part of a plea deal.

The 39-year-old was identified in video footage taken inside the Capitol Building, in part because he was wearing a United States Olympic Team jacket.

Five people, including a police officer, died during the riot on January 6, when supporters of former US President Donald Trump stormed the Capitol Building, attempting to stop Joe Biden become the new American President.

Keller earned two Olympic gold medals and one silver with the American men's 4x200 metres freestyle relay team, triumphing at Athens 2004 and Beijing 2008 and finishing second at Sydney 2000. 

The 38-year-old also claimed bronze medals in the men's 400m freestyle at Sydney 2000 and Athens 2004.

Keller was known to be a Trump supporter and commercial real estate firm Hoff and Leigh issued a statement after the riot stating that Keller, an independent contractor, had resigned in the wake of the incident.

Both the US Olympic and Paralympic Committee and USA Swimming condemned the riot.