Biles's Olympic fate in balance as support pours in

Simone Biles was mulling her Olympic future on Wednesday as athletes and public figures led an outpouring of support after her decision to withdraw from the women's team gymnastics event over mental health concerns.

US icon Biles, widely regarded as the greatest gymnast of all time and one of the biggest stars at the Tokyo Games, shocked the sporting world on Tuesday after abruptly pulling out of the team final following a lacklustre opening vault.

The 24-year-old four-time Olympic champion later revealed she abandoned the competition due to concerns for her mental wellbeing.

"I have to focus on my mental health," Biles said. "I didn't want to go out and do something stupid and get hurt... At the end of the day we don't want to be carried out of there on a stretcher."

Biles' decision has been widely hailed as a game-changing moment for elite sport, helping to dispel enduring stigmas surrounding mental health.

It was unclear whether she plans to compete in the remainder of the Olympics.

She is due to defend her individual all-around title on Thursday, and is also qualified for the individual apparatus finals on Sunday.

Biles said late Tuesday she would assess her readiness to compete on a "day-by-day" basis.

"Physically, I feel good, I'm in shape," she said on NBC television's Today program. "We're going to take it day by day, and we're just gonna see."

As Biles reflected on her remaining competition schedule, she drew broad support from athletes, officials, sports officials and public figures.

"Simone, you've made us so proud. Proud of who you are as a person, teammate and athlete," tweeted Sarah Hirshland, US Olympic and Paralympic Committee chief executive officer.

"We applaud your decision to prioritize your mental wellness over all else and offer you the full support and resources of our Team USA community as you navigate the journey ahead."

Former US first lady Michelle Obama tweeted: "Am I good enough? Yes, I am. The mantra I practice daily. @Simone_Biles , we are proud of you and we are rooting for you."

Two-time Olympic Alpine ski champion Mikaela Shiffrin offered support as well, tweeting: "@Simone_Biles keep whipping out that smile of yours cause it is undeniably golden. Always."

Filipino boxing legend Manny Pacquiao tweeted: "Once a champion, always a champion. God Bless @Simone_Biles."

US swimming and Olympic legend Michael Phelps, who in 2018 revealed his own struggles with depression and suicidal thoughts following the 2012 Olympics, said watching Biles struggle on Tuesday "broke my heart."

Phelps told NBC the Olympics could be overwhelming for athletes, and that he had often struggled to find support during his own career.

"The biggest thing is we all need to ask for help sometimes too when we go through those times," Phelps said. "For me, I can say personally it was something very challenging. It was hard for me to ask for help.

Biles's former USA teammate Aly Raisman spoke of her concerns for her friend's wellbeing.

"I know that all of these athletes dream of this moment for their whole entire lives, and so I'm just completely devastated," Raisman told NBC.

"I am obviously so worried and just hoping that Simone is OK."

Raisman and Biles were among the gymnasts abused by former US team doctor Larry Nassar, who was jailed in 2018 for sexual abuse.

"It's just so much pressure, and I've been watching how much pressure has been on her in the months leading up to the Games, and it's just devastating. I feel horrible," Raisman added.