NEW YORK: The US Olympic and Paralympic Committee has defended its handling of the Larry Nassar case after several top gymnasts who suffered sexual abuse under the former team doctor's care sent a letter to Congress calling for the USOPC board to be dissolved.

Olympic gold medallists Simone Biles, McKayla Maroney and Aly Raisman, along with World Championships gold medallist Maggie Nichols, sent the letter on Wednesday saying the "Board's past actions demonstrate an unwillingness to confront endemic problems with abuse," according to media reports.

The four were among the dozens of accusers who came forward against Nassar, who was sentenced to up to 175 years in prison in 2018 for sexually assaulting gymnasts entrusted to his care.

"The letter addressed to Congress underscores their concern, and we recognise the bravery of the athlete survivors who continue to bring these issues forward," the USOPC said in a written statement provided to Reuters.

"The letter references issues that USOPC has been addressing for more than two years –- and the work we continue to do every day."

The USOPC also said it had "implemented the most sweeping governance reforms in nearly two decades" and was "fully committed to addressing sexual abuse at every level of sport".

Gymnasts including Biles, Maroney and Raisman appeared before a Senate panel last month, where they excoriated the FBI for failing to investigate the matter properly.

The US Justice Department launched a fresh inquiry into the FBI's botched handling of its investigation into Nassar earlier this month, after previously declining to prosecute the agents involved.