Reigning world and Olympic all-around gymnastics champion Simone Biles of the U.S. says coping with the mental strain of waiting another year for the Tokyo Olympics will take a heavy toll by 2021.

Biles, who turned 23 last month, told the Today show on U.S. Olympic telecaster NBC that she expects coaches will have her in top condition, but getting her mind in top shape in July a year later than planned will be difficult.

"Physically I have no doubt that my coaches will get me back in shape," Biles said. "But mentally going another year, I think that's what's going to take a toll on me and all of us, most of the athletes."

"So we have to stay in shape mentally as much as physically, and that will play a big factor moving forward, listening to your body and your mind."

Biles told the Wall Street Journal she was planning to retire after the Tokyo Olympics this year and is playing next year's Games "by ear."

Biles won all-around, vault, floor and team gold at the 2016 Rio Olympics and owns five all-around world titles among her 19 world titles since 2013.

After taking off 18 months following Rio, Biles returned to top form with a goal of success in July in a sport that has dominated much of her time since she first tried it at age six.

Then came the COVID-19 pandemic and the decision to postpone the Tokyo Olympics for one year, a delay she learned about on her phone in the locker room during training.

"I didn't really know what to feel," Biles said. "I just kind of sat there. I cried. But ultimately it was the right decision."

"We need to make sure that everyone in the U.S. and around the world is healthy and safe. It was hard, but it's OK."