Caster Semenya could go head-to-head with current world champion Dina Asher Smith at the Tokyo Olympics after the South African announced her intention to switch to the 200 metres.

Semenya is barred from defending her Olympic 800m crown without submitting to performance-reducing drugs in a rule introduced by the sport's governing body.

But the rule does not apply over shorter distances and the 29-year-old says she will switch her target to a distance in which Asher Smith was crowned world champion this year.

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In a statement posted on her Instagram page, Semenya wrote: "My dream has always been, and will continue to be, to compete at the highest level of sport and so in order to pursue my goals and dreams I have decided to change events and compete in the 200m.

"This decision has not been an easy one but as always I look forward to the challenge and will work hard, doing all I can to qualify for Tokyo and compete to the best of my ability for South Africa.

"Thank you to my team who have supported me over the past few months and thank you to all South Africans who believe in me and stand behind me."

Semenya has rejected the IAAF's conclusion that without taking the now-required medication, she would have an unfair "competitive advantage" over the longer distance.