Nassar, who appeared for a plea hearing at Ingham County Court in Lansing in Michigan, was charged with molesting seven girls during his time with the governing body.

All but one of his accusers are gymnasts, while three of them were under the age of 13.

The offences, which occured between 1998 and 2015, took place at his home and at his clinic in Michigan.

Olympic gold medallists Aly Raisman, McKayla Maroney and Gabby Douglas are among those to have accused the 54-year-old of sexual abuse when he served as the doctor for the American team.

Under the plea deal, Nassar, who has been accused of molesting around 130 women, will serve at least 25 years in prison but the judge could impose a sentence as high as 40 years.

He is now due to be sentenced on January 12.

Nassar is also facing federal charges of receiving child pornography, possessing child pornography and a charge that he hid and destroyed evidence in the case. 

A separate hearing is scheduled to be held on Monday (November 27). 

During the plea hearing, Nassar apologised for his actions, which alleged victim Larissa Boyce described as "evil".

"For all those involved, I’m so horribly sorry," Nassar said, according to ESPN. 

"This is a match that turned into a forest fire, out of control. 

"I pray the rosary every day for forgiveness. 

"I want them to heal. 

"I just want healing."

Ingham County Court Judge Rosemarie Aquilina said Nassar had used his position of trust "in the most vile way - to abuse children".

"You violated the oath that you took, which is to do no harm, and you harmed them," she said.

"Selfishly.

"I agree that now is a time of healing, but it may take them a lifetime of healing while you spend your lifetime behind bars thinking about what you did in taking away their childhood."

Raisman, a three-time Olympic champion who was part of the gold medal winning teams at London 2012 and Rio 2016, tweeted during the hearing that it was "disgusting"  that Nassar was referred to a doctor.

It came after Douglas became the latest American gymnast to speak out yesterday.

Jessica Howard, the US national rhythmic gymnastics champion from 1999 to 2001, and Jeanette Antolin, a Pan American Games silver medallist, also revealed in February they had been the victim of sexual abuse on the 60 Minutes programme.

Atlanta 1996 gold medallist Dominique Moceanu and Sydney 2000 bronze medallist Jamie Dantzscher joined Howard in testifying in March to a Senate Committee in Washington D.C., with the aim of protecting young athletes from abuse.

Dantzscher also filed a lawsuit against Nassar in California last September as "Jane Doe".

The scandal in the sport led to the resignation of USA Gymnastics chief executive Steve Penny in March of this year.

Penny has since been replaced by Kerry Perry as President and chief executive, while USA Gymnastics have also undergone an independent review.

It was commissioned by USA Gymnastics and conducted by Deborah Daniels, a former Federal prosecutor, who spent a significant portion of her career prosecuting child sexual offenders, and scrutinised the organisation's methods.

USA Gymnastics approved a new safe sport policy as a result of the recommendations made by the review.

In a statement, USA Gymnastics said they were "very sorry" that Nassar had harmed the athletes.

They added that they viewed Nassar's guilty plea as an "important acknowledgment of his appalling and devious conduct that permits punishment without further victimisation of survivors".