Simone Biles will not defend her Olympic title in Thursday's individual all-around competition in order to focus on her mental health, USA Gymnastics has confirmed.

The four-time gold medallist from Rio completed only one event in Tuesday's team competition at the Ariake Gymnastics Centre, registering the lowest score of the first rotation.

Biles left the floor with a trainer and, although she later returned donned in a tracksuit, she opted not to continue and remained to support her team-mates who could only secure silver behind the Russian Olympic Committee.

Following the team event, Biles opened up on her struggles at Tokyo 2020 and said she would take it day-by-day before making a decision.

USA Gymnastics subsequently announced she will not participate on Thursday and will continue to be evaluated before a decision is made on whether she takes part in the individual event finals, which take place next week.

"After further medical evaluation, Simone Biles has withdrawn from the final individual all-around competition at the Tokyo Olympic Games, in order to focus on her mental health," a USA Gymnastics statement read.

"Simone will continue to be evaluated daily to determine whether or not to participate in next week’s individual event finals. Jade Carey, who had the ninth highest score in qualifications, will participate in her place in the all-around."

USA Gymnastics hailed Biles for her decision to put her own well-being ahead of competing.

"We wholeheartedly support Simone's decision and applaud her bravery in prioritising her well-being," the governing body added.

"Her courage shows, yet again, why she is a role model for so many."

. @Simone_Biles you’ve pushed boundaries time and time again. Rest up & take time pic.twitter.com/ktAmF0UmAc

— Max Whitlock MBE (@maxwhitlock1) July 28, 2021

The decision for Biles not to continue was initially described as a "medical issue", though the 24-year-old later confirmed she is not injured.

She said she has been "fighting demons" and added: "I just don't trust myself as much as I used to. I don't know if it's age. I'm a little bit more nervous when I do gymnastics. I feel like I'm also not having as much fun."

At a follow-up news conference, Biles offered an inspirational message on the importance of protecting mental health, while her actions drew widespread support on social medial

"I say, 'put mental health first'," Biles said. "Because if you don't, you won't enjoy sport and won't succeed as much as you want to.

"So it's okay sometimes to sit out the big competitions to focus on yourself, because it shows how strong a competitor and person that you really are, rather than just battling through it."

Biles is one of the premier attractions at Tokyo 2020 and entered the Games with the possibility of winning six gold medals, a haul which would have represented the most at a single Olympics.

She is slated to compete in the beam, uneven bars, vault and floor exercise in the individual events next week.