Sha'Carri Richardson won the 100m at the US trials in Oregon in JuneUS sprinter Sha'Carri Richardson has received a one-month ban after testing positive for marijuana - and is set to miss the Tokyo Olympics.
The 21-year-old won the 100m at the US Olympic trials in Oregon in June and earlier this year ran the sixth-fastest time in history.
But the Texan's positive test means her qualification result has been expunged.
"Don't judge me, because I am human, I just happen to run a little faster," she told NBC's Today show.
The athlete's positive test came at the Olympic trials event, where she finished well clear of the field in 10.86secs
The trials came just a week after the death of her biological mother, and Richardson explained she had used cannabis as a way of coping.
"I apologise for the fact that I didn't even know how to control my emotions or deal with that during that time," she told the US broadcaster on Friday.
As Richardson was giving her interview, the US Anti-Doping Agency (Usada) announced she had accepted the suspension for what it said was "a substance of abuse" rather than for enhancing performance.
"The rules are clear, but this is heartbreaking on many levels," said Usada chief executive 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."
The ban is dated from 19 June.
In theory she could be free to compete at the Olympics as her suspension ends before Tokyo's track and field programme begins on 30 July.
But her results at the trials have been wiped out and Usada said her eligibility for Tokyo would be a decision for US Track and Field (USATF) and the US Olympic and Paralympic Committee.
When asked whether she still hoped to take part in the Games, Richardson said she would focus on herself, and suggested she would not be competing in Tokyo.
"I greatly apologise if I let you guys down - and I did. This will be the last time the US comes home without a gold in the 100m," she added.
"I'm 21, I'm very young, I have plenty of Games left in me to compete in and plenty of talent that backs me up because everything I do comes naturally to me, no steroids or anything.
"This incident was about marijuana so after my sanction is up I'll be back. Next time I step on the track I'll be ready for whatever anti-doping agencies come and [they will] get whatever they need because this will never happen again."
USATF said it would be supporting the sprinter.
"Sha'Carri Richardson's situation is incredibly unfortunate and devastating for everyone involved," it said. "Athlete health and well-being continue to be one of USATF's most critical priorities and we will work with Sha'Carri to ensure she has ample resources to overcome any mental health challenges now and in the future."
Cannabis is prohibited by the World Anti-Doping Agency, and carries a ban of up to four years.
However, that can be reduced to three months if athletes can show taking it was not related to sports performance.
Any ban can be reduced further still, to one month, if athletes agree to a treatment programme.
