South African double Olympic champion Caster Semenya. Picture: Noushad Thekkayil/EPA/African News Agency (ANA)

LAUSANNE – The Court of Arbitration for Sport said Thursday that it was delaying until next month its ruling on a challenge filed by South African double Olympic champion Caster Semenya against the IAAF.

A decision in the controversial case had been due next week, but the world's top sport court said it would not issue a verdict “until the end of April” because both sides had filed additional material since the hearing in February. 

“No precise date has been set,” said a CAS press release.

Semenya is challenging proposals by the International Association of Athletics Federations that aim to restrict female athletes' testosterone levels.

The IAAF is looking to force so-called “hyperandrogenic” athletes or those with “differences of sexual development” (DSD) to seek treatment to lower their testosterone levels below a prescribed amount if they wish to continue competing as women.  

The court is set to rule on capping testosterone levels in women athletes at five nanomoles per litre (nmol/L) of blood.

The athletics governing body has argued the moves are necessary to create a “level playing field” for other female athletes.

In a statement sent to AFP, the IAAF responded to the delay by saying: “the postponement will not prejudice the athletes concerned.”

The IAAF also said it was establishing a “special transitional provision” allowing those who “respect the limit of 5 nmol/L, as of the week following the publication of the decision” to be eligible for the athletics World Championships which start in Doha on September 28.

A wide coalition has rallied behind Semenya's cause, including the government in her native South Africa and rights activists worldwide. 

Some scientific experts have argued that barring Semenya from competition due to naturally high testosterone levels would be like excluding basketball players because they are too tall.

Agence France-Presse (AFP)