xAthletics chiefs have denied reports they want women's 800m champion Caster Semenya classified as 'biologically male' - but say she should be made to reduce her testosterone levels.
The Court of Arbitration for Sport is due to hear Semenya's landmark case next week in Lausanne.
The IAAF denied it was seeking to have any athlete with differences in sexual development (DSDs) classified as male, saying it 'accepted their legal sex without question'.
However, the governing body added that it wants athletes such as Semenya, who was born with testes, to reduce their testosterone levels before they compete internationally.
Sports scientist Ross Tucker told the Guardian Semenya could be 'five to seven seconds slower' in the 800m if her testosterone levels were brought down.
In a statement, the IAAF said: 'The IAAF is not classifying any DSD (Differences of Sexual Development) athlete as male.
'To the contrary, we accept their legal sex without question and permit them to compete in the female category.
'However if a DSD athlete has testes and male levels of testosterone, they get the same increases in bone and muscle size and strength and increases in haemoglobin that a male gets when they go through puberty, which is what gives men such a performance advantage over women.