Simone Biles' Tokyo Olympics future was in doubt after she dropped out of the women's team final after one vault as the United States lost out on the gold medal to Russia.

After a disappointing performance that saw her exit the evening's competition, Biles said she was unsure whether she would compete on Thursday in the women's all-around event.

"After the performance I did I just didn't want to go on," said Biles, fighting back tears as she met with the media. "We are going to see about Thursday.

"I'm just trying to gear up for the next test."

The 24-year-old later confirmed she was not suffering a physical injury, and had decided to take a step back because she feared she would not be able to contribute to her team’s pursuit of a third consecutive team gold medal.

"I just felt it would be a little bit better to take a back seat and work on my mindfulness," said Biles in a remarkably honest interview following the competition, in which the US were pipped to gold.

"No injury, thankfully. That’s why I took a step back because I didn’t want to do something silly out there. I thought it was best if these girls took over. I knew they would be okay."

It was a stunning and disappointing start to the Olympics for the US women, who had expected to dominate the final as they had not been beaten in a major team competition since 2011.

But the entire event was turned on its head in an instant when Biles, the world and Olympic all-around champion, completely mistimed her opening vault to earn a low score of 13.766.

It was a setback the US never recovered from as Russia, competing as representatives of the Russian Olympic Committee (ROC) because the country was stripped of its flag and anthem for doping offences, claimed the team title for the first time since the Unified Team at the 1992 Barcelona Games.

The US, winners in 2012 and 2016, settled for silver and Britain claimed the bronze.

There were signs Biles had been struggling to deal with the high level of pressure.

Simone Biles of Team United States stumbles upon landing

At the US Olympic Trials in June she was left in tears when she was unable to come to grips with the disappointment of her performance.

The pressure of chasing medals continued to build in Tokyo, Biles posting on social media after Sunday's uninspired qualification effort that she felt she was carrying the weight of the world.

"It wasn't an easy day or my best but I got through it," Biles wrote on Instagram. "I truly do feel like I have the weight of the world on my shoulders at times.

"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!"

Biles has qualified for every event in Tokyo and along with the all-around is scheduled to contest four apparatus finals during the second week.

Six golds are now out of reach but Biles could still equal the record of nine held by Russian gymnast Larisa Latynina over three Olympic Games - Melbourne 1956, Rome 1960 and Tokyo 1964.

But she hinted some things are more important than medals.

"I do not trust myself anymore," said Biles. "I tried to go out there for the team and they stepped up to the plate
"I have to focus on my mental health."

Despite taking a single vault, Biles will add a silver medal to the five she won at the Rio 2016 Games, including four golds.

But her bid to become the greatest female Olympian of all-time with 10 golds is over.

Biles, second from left, on the podium with her team-mates after winning silver

Biles's competition got off to a poor start on the vault in the first rotation. All three Russians scored higher, as did her US team-mates.

Stunned and close to tears, Biles, gold medal winner on the vault at the Rio Olympics, sat dejected in a chair as coaches and team mates surrounded her before moving onto the uneven bars, the US sitting second, 1.067 behind their Russian rivals.

Biles, however, appeared to be more than simply disappointed, leaving the arena with the trainer as her team mates warmed up.

By now coaches and officials sprinkled throughout the Ariake Gymnastics Centre had begun to chatter as Biles reappeared minutes later slipping into her warm-up gear.

While Biles left the arena uncertain if she would be back some of here fellow gymnasts said they fully expect to see her on Thursday.

"This is very unusual for her, but if you’re under a lot of pressure it can affect your body," said Japan's Mai Murakami. "I think she decided to save her body for later this week, for the all-around and apparatus."