Superstar gymnast Simone Biles says she is feeling the pressure of competition after the U.S. women's gymnastics team posted lower-than-expected scores during qualifiers on Sunday.

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

"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!" she added.

The U.S. team came out one point behind Russia in the gymnastics qualifying rounds, which determine the teams that make it to the finals.

Although the scores from the qualifiers don't carry over into the gymnastics final scheduled for Tuesday, the results were still a surprise for a team heavily favored to dominate the competition.

"I feel we did a pretty good job," Biles told reporters after the Sunday qualifiers. "Obviously there are little things we need to work on, so we'll go back and practice and work on that, just so we can do our best performance at team finals, because that's what matters."

Nevertheless, an imperfect performance by a gymnast largely hailed as the best of all time was still a strong showing.

Biles scored higher than her U.S. teammates in the floor exercise and vault, and she nabbed second place in the uneven bars and balance beam.

In her Instagram post, Biles said she was happy that her family could join her virtually for the competition. "[T]hey mean the world to me!"

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