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The new boss of US gymnastics says she "regrets" a month-old tweet which appeared to criticise Nike's decision to make NFL star Colin Kaepernick the face of their new advertising campaign.

Mary Bono, 56, had tweeted a picture of herself colouring in the Nike logo.

Quarterback Kaepernick protested against racial injustice by kneeling during the US national anthem.

US four-time Olympic champion gymnast Simon Biles expressed her surprise at Bono's post, "Mouth drop."

Biles, who is sponsored by Nike, added: "It's not like we needed a smarter US gymnastics president or any sponsors or anything."

Former congresswoman Bono was appointed interim boss on Friday, as a temporary replacement for Kerry Perry, who resigned in September, nine months into the job, after being criticised for her handling of the fallout from the Larry Nassar abuse scandal.

Biles told the ´óÏó´«Ã½ last week it was a "relief" and "empowering" to speak out about being the victim of sexual abuse by jailed US Gymnastics team doctor Nassar.

In January, Nassar was sentenced to up to 175 years after nearly 160 women accused him of sexual abuse.

Responding to her own initial tweet, "I regret the post and respect everyone's views and fundamental right to express them.

"This doesn't reflect how I will approach my position at USA Gymnastics. I will do everything I can to help build, with the community, an open, safe and positive environment.

"I know the tweet will live on but have taken it down to move the focus to all I hope to accomplish on behalf of a great sport and those who are dedicated to it."