Tokyo Olympics: 'Rules are rules' - US President Joe Biden scolds sprinter Sha'Carri Richardson over cannabis ban

US President Joe Biden has weighed in on the suspension of sprinter Sha'Carri Richardson over marijuana use, saying "the rules are the rules".

The US Anti-Doping Agency (USADA) confirmed Richardson's suspension, after the sprinter known for brightly-coloured hair and record-breaking speed tested positive for cannabis during her 100m trials in June.

The women's 100m event at the Tokyo Olympics starts on July 30, two days after Richardson's ban ends, but the adverse finding means her qualifying results at the trials, which offer automatic places to the first three qualified athletes in each event, are annulled.

"The rules are the rules and everybody knows what the rules were going in," Biden says. "Whether they should remain the rules is a different issue, but the rules are the rules."

Richardson's suspension provoked bipartisan critiques in Washington. Democratic Representative Alexandria Ocasio-Cortez called on USADA to "strike a blow for civil liberties" by overturning the suspension.

"Let her compete," tweeted Donald Trump Jr, the former Republican president's son. "I'm pretty damn sure weed has never made anyone faster."

Cannabis is on the list of substances banned by the World Anti-Doping Agency. USADA says it reduced the typical three-month ban to one month, because Richardson used cannabis outside of competition and she had successfully completed a counseling programme.

Richardson has told NBC's Today Show that the episode came as she was coping with her mother's death.

"This incident was about marijuana, so after my sanction is up, I'll be back and able to compete, and every single time I step on the track, I'll be ready for whatever anti-doping agency to come and get what it is that they need," she says.

Biden says he's "really proud of the way she responded".