Simone Biles withdrew from the vault and uneven bar apparatus finals at the Tokyo Olympics on Saturday as the U.S. gymnast continued to wrestle with mental health issues. 

"Today, after further consultation with medical staff, Simone Biles has decided to withdraw from the event finals for vault and the uneven bars," said USA Gymnastics in a statement. "She will continue to be evaluated daily to determine whether to compete in the finals for floor exercise and balance beam." 

Biles had earlier made a shock exit at the Games when she dropped out of the team competition following a poor opening with an uncharacteristic balk on vault and then decided not to defend her all-around crown. 

The 24-year-old, however, might yet make another appearance at the Tokyo Games having not ruled herself out for floor exercise on Monday and beam on Tuesday. 

Biles was expected to be one of the headliners of the Tokyo Games in a bid for six gold medals that would have made her the most successful woman Olympian of all-time across every sport. 

Biles said 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. 

"It's honestly petrifying trying to do a skill but not having your mind & body in sync," Biles wrote on Instagram on Friday. 

The decision to drop out of two more finals means Biles will not defend the vaulting gold she won at the 2016 Rio Olympics. 

MyKayla Skinner, who had the fourth highest score in vault during qualifications, will compete in vault finals for the U.S. alongside Jade Carey, who finished with the second highest score. 

Sunisa Lee will now be the only American competing in the uneven bars final, who won the all-around title on Thursday. 

(With input from agencies)