Biles takes aim at USA Gymnastics in birthday tweet

Four-time Olympic gold medallist Simone Biles wants more than good wishes from USA Gymnastics.

The US federation wished Biles a happy 23rd birthday on social media on Saturday.

Biles -- who also owns 19 world titles and is expected to be among the stars of the Tokyo Olympics -- used their tweet as a chance to demand an independent investigation into the Larry Nassar sex abuse scandal.

"How about you amaze me and do the right thing ... have an independent investigation," Biles snapped on Twitter after the federation's birthday tweet.

"HAPPY BIRTHDAY to the most decorated gymnast of all time, @simonebiles!" USA Gymnastics wrote, posting a video of Biles in action in a floor exercise.

"We know you will only continue to amaze us and make history!" Former national gymnastics team doctor Nassar was jailed for life for abusing more than 250 athletes, including stars of the United States' 2012 and 2016 gold medal-winning Olympic teams.

A US Senate investigation found that "multiple institutions" failed to adequately respond to credible allegations against Nassar, but Biles has said that USA Gymnastics and the US Olympic and Paralympic Committee still owe his victims, including herself, more answers and a framework to ensure such abuses won't occur again.

"Wish they BOTH wanted an independent investigation as much as the survivors & I do," she tweeted earlier this month.

As Biles and other elite gymnasts ramp up their preparations for Tokyo, USA Gymnastics in January offered a $215 million (194 million euros) settlement to victims of Nassar to settle legal claims -- a plan a lawyer for more than 200 women called "unconscionable."