Simone Biles out of team competition early in Tokyo

Simone Biles left competition early at the Tokyo Olympics team competition Tuesday after a rare stumble on vault.

She will not be competing in the rest of the competition for the team event.

USA Gymnastics said in a statement, "Simone has withdrawn from the team final competition due to a medical issue. She will be assessed daily to determine medical clearance for future competitions."

NBC had reported earlier that her coach said she withdrew due to a "mental issue." Details were not immediately clear.

All eyes were on Biles to see if she would attempt a Yurchenko double pike on vault. Instead, as the Americans opened competition on vault, Biles bailed in the middle of her Amanar attempt, bringing down the difficulty level of her vault.

Rather than 2.5 twists, she only did 1.5, resulting in a score of 13.766 -- remarkably low for Biles' standard. The Americans ended that first rotation, out of four, about a point lower than the athletes from Russia.

After that vault, Biles spoke with her coach and a trainer. She left the competition floor and returned as her teammates were preparing for uneven bars. She has since stood by her team, wearing sweats and cheering them on.

The U.S. women's gymnastics team is competing in the team finals at the Tokyo Olympics on Tuesday, seeking to bring home the gold for the third time in a row.

This is one of the strongest gymnastics teams the world has seen, led by all-time great Biles and uneven bars phenom Sunisa Lee. The team is rounded out by Jordan Chiles, who's powerful on floor, and Grace McCallum.

During qualifiers for the final this past weekend, the Americans were surpassed by athletes from Russia competing under the Russian Olympic Committee (ROC).

The U.S. ended with a cumulative score of 170.562, while the athletes from Russia finished with 171.629. While those numbers do not factor into the finals scores, it sent a message to the previously dominant American team.

"I truly do feel like I have the weight of the world on my shoulders at times," Biles posted on Instagram after the qualifying event. "I know I brush it off and make it seem like pressure doesn't affect me but damn sometimes it's hard hahaha! The olympics is no joke!"

The U.S. has medaled in every women's gymnastics team event at the Olympics since 1992. That included three golds, two silvers and two bronzes.

In the team event, three athletes from a four-person team compete on each apparatus. For the women, this includes balance beam, uneven bars, vault and floor.

The U.S. men's gymnastics team came in fifth at their final Monday.

Both individual American men and women will have more opportunities for medals as the all-around and apparatus finals take place later in the Games. While Biles had qualified for those individual events, it remains to be determined if she will be able to compete.

For more Olympics coverage, see: https://abcnews.go.com/Sports/Olympics