Hurdler CeCe Telfer will not be allowed to compete in the U.S. Olympic trials this week because she has not met World Athletics standards for transgender athletes, USA Track and Field said.
Telfer had hoped to participate in the women's 400 metres hurdles, the qualifying rounds for which are scheduled for Friday at the trials in Eugene, Oregon.
"While CeCe Telfer has met the performance qualification standard, she has not met the conditions established in the World Athletics 'Eligibility Regulations for Transgender Athletes' and is therefore ineligible to compete," USA Track and Field said in a statement.
The regulations require a transgender athlete to reduce testosterone to below a certain level for 12 months before competing in women's events.
Athletes must meet the requirements to participate in the U.S. trials and be a member of the U.S. Olympic team.
Two-time Olympic gold medallist Caster Semenya of South Africa, who is a cisgender woman, has sought unsuccessfully for years to overturn the regulations, which were established in 2019 and have precluded her from competing in any race from 400m to a mile due to her naturally elevated testosterone levels.
Telfer, who was born in Jamaica, competed in the men's 400m hurdles in the U.S. collegiate Division II championships in 2016-17 and won the women's title in 2019.
USATF said World Athletics had notified it on June 17 that Telfer had not met the conditions and after a subsequent notification from the world governing body, the athlete was given the opportunity to demonstrate her eligibility.
She was been unable to do so, USATF said.
"USATF strongly supports inclusivity and providing a clear path to participation in the sport for all, while also maintaining competitive fairness," the U.S. federation said.
"If CeCe meets the conditions for transgender athlete participation in the future, we wholeheartedly back her participation in international events as a member of Team USATF."
World Athletics said: "It's our policy not to comment on individual cases due to medical confidentiality."