MONACO (AP):

Track and field authorities in South Africa say they are prepared to go to the Court of Arbitration for Sport (CAS) to challenge new rules that could sideline women with high natural testosterone levels from middle-distance races.

Athletics South Africa calls the rules "skewed" and says that if the IAAF upholds them, "we will proceed to CAS for further assistance on the matter".

Two-time Olympic 800m champion Caster Semenya of South Africa is the highest-profile athlete expected to be impacted by the rules that divide expert opinion.

The IAAF argues that women with unusually high testosterone levels have a competitive advantage over other women. It intends, from November 1, to limit entry for all international events from 400m through the mile to women with testosterone levels below a specified level.