Lawyers for the International Association of Athletics Federations will tell a court Olympic women's 800m champion Caster Semenya should be classed as a "biological male" who identifies as female next week.
While the IAAF will argue the 28-year-old South African should be classed as "biologically male" they will also suggest Semenya be allowed to compete in women's races if she takes testosterone suppressants, The Times reports.
The issue will be addressed in a five-day hearing at the Court of Arbitration of Sport seen as a landmark case surrounding athletes with differences of sexual development (DSD).
It's a case that will further bring the use of testosterone blockers into the spotlight. In 2018, the United Nations human rights special procedures body implored the IAAF to drop their regulations when it came to transgender athletes and testosterone blockers, claiming they "contravene international human rights."
Speaking to The Times, IAAF lawyer Jonathan Taylor said if the case went against them it would be a blow to athletes with normal female levels of testosterone, which are an average 15 times lower than the normal male range.
"If the CAS rules that legal recognition as female is sufficient to qualify for the female category of competition, and the IAAF is not permitted to require athletes of female legal sex who have testes and consequently male levels of testosterone to reduce those levels down to the female range, then DSD and transgender athletes will dominate the podiums and prize money in sport, and women with normal female testosterone levels will not have any chance to win," Taylor said.
Independent legal experts told The Times the IAAF's case is much stronger now than when it lost a ruling brought by the Indian sprinter Dutee Chand in 2015.
Semenya is challenging the IAAF's new eligibility rules that would mean DSD runners in women's middle-distance races would have to have less than five nanomoles of testosterone per litre (nmol/L) of blood for the previous six months, or to race against other DSD athletes or men.
In 2018, Dr Ross Tucker from the University of Cape Town estimated Semenya's time for the 800m would drop by five to seven seconds if she was forced to inhibit testosterone to the level of the IAAF's new eligibility rules.