World Cup winning US midfielder Megan Rapinoe said the "murderous mob" of President Donald Trump's supporters who stormed the Capitol last week showed the country's true colours.

At least five people died in the attack after hundreds of the president's followers breached the Capitol while Congress worked to certify Joe Biden's victory in November's presidential election.

"This was about white supremacy and holding up white supremacy," Rapinoe told reporters.

"Hopefully (it's) the final straw for so many people to really understand the reason we're here is because we never have actually had a reckoning with what our country really is.

"I think we showed very much our true colours. This is not the first time we've seen a murderous mob like that."

Rapinoe, speaking at US women's national team training camp in Orlando, said there had to be accountability and punishment before the healing process could begin.

"All the calls for unity and moving forward cannot come without justice," she added. "If we do not punish this and investigate this to the fullest extent, it only encourages more of this to happen.

"So anybody thinking, 'Oh well, they really wouldn't have done that much and we should give them sort of a pass'. Maybe we haven't seen this in our lifetimes.

"But we should make no mistake about what the intent was. It was a murderous moment. Five people are dead ... we can't bring them back."

The FBI has opened 160 case files in its investigation of the storming of the Capitol, the head of the agency's Washington field office said on Tuesday.

On Tuesday, the president said his remarks in a speech to his followers before they attacked the Capitol were "totally appropriate".