Caster Semenya's lawyers say the Olympic champion is "optimistic" of victory in her appeal against IAAF rules designed to control naturally high levels of testosterone in female athletes.

South African Semenya's lawyers said in a statement Friday that "she remains optimistic the Court of Arbitration for Sport will declare the IAAF's regulations unlawful, invalid and of no effect."

The rules proposed by track and field's governing body, which haven't yet come into effect, would require female athletes with naturally high levels of testosterone to lower those levels either by medication or surgery in order to be eligible to compete at top track meets. The rules would apply to distances ranging from 400 meters to one mile.

The lawyers said a victory for Semenya at the CAS would "prevent women athletes from ever having to undergo medical interventions in an attempt to comply with these regulations."

The statement from Semenya's lawyers came a day after the CAS, sport's highest court, said a decision in the pivotal case would be delayed until the end of April to allow for more legal debate. The delay is down to extra evidence submitted by both sides. Semenya's lawyers confirmed she had made additional submissions "in response to post-hearing communications from the IAAF."

Semenya is a two-time Olympic and three-time world champion in the 800 meters. She's the most famous of a number of female athletes who have high levels of naturally occurring testosterone. The IAAF argues that gives them an unfair advantage over other female athletes.

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