Caster Semenya, who will make her first appearance in a world championships in five years when she competes in the women's 5000m in Eugene, has every right to be there, World Athletics president Sebastian Coe said Tuesday.

The South African last competed at a world championships in London in 2017 where she won her third 800m world crown.

A year later she won double gold in the 800m and 1500m at the Commonwealth Games which is the last time she represented South Africa in a global international competition.

Semenya was forced to switch from her favoured distance to the longer event due to gender eligibility rules that required her to take testosterone-reducing drugs to compete in races between 400m to a mile.

World Athletics bars women athletes with high testosterone levels from competing in shorter races because the governing body says the hormone increases muscle mass and oxygen uptake.

Semenya, who became a world champion at 18 years of age in Berlin in 2009, has made several unsuccessful legal attempts to overturn the ruling.

"She's eligible to be here," Coe said of Semenya, who initially missed qualification when she only finished sixth at the African Championships last month, but has benefitted from a number of athletes dropping out.

"If she chooses to compete in a distance that is not a restricted distance that's entrirely up to her and she'll get the same treatment and same services as any athlete that's legitimately here," which she is.

Semenya is just one of a handful of "restricted" athletes in Oregon, but Coe insisted he didn't want "these athletes to go away any time soon".

"My whole approach to this has actually been about inclusivity. I didn't come into the sport to stop people competing."

South Africa's Caster
South Africa's Caster AFP / Fabien Dubessay

But Coe, who won two 1500m Olympic gold for Britain in 1980 and 1984, stressed that gender eligibility rules would not be changed any time soon.

"We've always been guided by the science and science is pretty clear: we know that testosterone is the key determinant in performance," he told news agencies.

"I'm really over having any more of these discussions with second-rate sociologists who sit there trying to tell me or the science community that there may be some issue. There isn't, testosterone is the key determinant in performance."

Coe added that it was his "responsibility to protect the integrity of women's sport".

"We have two categories in our sport: one is age and one is gender.

"Age because we think it's better that Olympic champions don't run against 14-year-olds in community sports and gender because if you don't have a gender separation no woman would ever win another sporting event."

Coe said current restrictions on events from the 400m to the mile were "not set in tablets of stone".

"If we find there's an impact in other events, we will have to take that into consideration," he said, adding that it was "not about an individual, not about a country, not about a continent".

When asked whether a widening of restrictions was likely, Coe responded: "I'm not going to speculate on that because I will be guided on the science.

"Only when we have really understood the impact beyond the restricted list, then that's on the table."