Simone Biles has pulled out of two more events at the Olympics, raising major doubts over whether she will compete again in Tokyo.
Biles came to Tokyo seeking five gold medals to equal the Olympic all-time gymnastics record of nine, but mental health issues prompted her to pull out of the team final on Tuesday and she did not take part in the all-around competition.
USA Gymnastics said the 24-year-old would sit out two more events.
"After further consultation with medical staff, Simone Biles has decided to withdraw from the event finals for vault and the uneven bars," the USAG statement said.
"She will continue to be evaluated daily to determine whether to compete in the finals for floor exercise and balance beam."
Biles said on Friday she was struggling with the "twisties", a mental block that has taken away her ability to perform the high-risk moves that she has trademarked.
The US federation said MyKayla Skinner would compete in the vault finals alongside Jade Carey.
"We remain in awe of Simone, who continues to handle this situation with courage and grace, and all of the athletes who have stepped up during these unexpected circumstances," the statement said.
Biles posted video on Instagram on Friday of her landing on her back in training, on cushioned pads, and wrote that she was having problems "literally on every event, which sucks".
She said previous bouts of 'twisties' had taken two or more weeks to pass, but there was "honestly no telling (the) time frame".
Biles, who was bombarded with messages of support after her earlier pull-outs, also hit back at critics, saying: "For anyone saying I quit, I didn't quit. My mind and body are simply not in sync as you can see here."