Sha'Carri Richardson has accepted a one-month ban from athletics.
The 21-year old sprinter tested positive for cannabis at the US Olympic trials on June 19.
One of the United States' main medal hopes at the Tokyo Olympics will therefore miss the 100m as her qualifying times from the meet at Eugene, Oregon will be struck from the record books.
Richardson won the 100m there in a time of 10.86.
She'd run the second fastest time in the world this year - 10.72 - at a meeting in Florida in April.
I am human
— Sha’Carri Richardson (@itskerrii) July 1, 2021
"The rules are clear, but this is heartbreaking on many levels," said USADA CEO Travis Tygart.
"Hopefully, her acceptance of responsibility and apology will be an important example to us all that we can successfully overcome our regrettable decisions, despite the costly consequences of this one to her."
Richardson's cannabis use came after she'd found out about the death of her biological mother.
After the US Trials race in Eugene, she revealed, "Last week, finding out my biological mother passed away and still choosing to pursue my dreams, still coming out here, still here to make the family that I do still have on this earth proud.
"And the fact [is] nobody knows what I go through. Everybody has struggles and I understand that, but y'all see me on this track and y'all see the poker face I put on, but nobody but them and my coach know what I go through on a day-to-day basis."
USADA say Richardson's ban began on June 28, but the door has been left ajar for her to represent the US in Tokyo.
While her 100m qualifying time has been struck out, she could still be eligible to race in the 4x100m relay.
As Guardian columnist Sean Ingle points out, the United States team brings the first four from the 100m trials and two discretionary picks.
It will therefore be up to US Track & Field to decide whether they want to bring her, as her ban will be up by the time action on the track begins. Round 1 of the women's 4x100m relay begins on August 5.
USADA's confirmation of Richardson's ban states, "Beyond the one-month sanction, athlete eligibility for the Tokyo Games is determined by the USOPC and/or USA Track & Field eligibility rules."
"I'm highly blessed and grateful... My family is my everything. My everything until the day I'm done."
Sha'Carri Richardson with so many emotions after earning a spot on the U.S. Olympic Team.@usatf | #TrackFieldTrials21 x #TokyoOlympics pic.twitter.com/8ujBpBSwVC
— NBC Olympics (@NBCOlympics) June 20, 2021