Washington: US ski star Mikaela Shiffrin says that "legitimate proof" of rights abuses in some Olympic host countries forces athletes to choose between their job and their morals, as calls mount for a boycott of the 2022 Beijing Games.

The build-up to next February's Winter Olympics has been overshadowed by concerns over the fate of China's Uighur minority in the Xinjiang region, where rights groups say at least one million Uighurs and other Turkic-speaking Muslims are incarcerated in camps.

The United States says that amounts to genocide. After initially denying the camps existed, the Chinese government abruptly acknowledged them, calling them vocational training centers aimed at reducing the allure of Islamic extremism.

Asked by CNN's Christina Macfarlane how "awkward" it was to compete at Games in countries such as China which have been accused of abuses, Shiffrin said: "What's a real bummer is that there's not only accusations, but legitimate proof in a lot of these places we've been going the last several Olympics."

The 2018 Winter Games were held in South Korea's Pyeongchang and four years earlier they took place in Russia's Sochi. Shiffrin won a gold medal at each.

The 25-year-old said that, with calls in some countries for athletes not to go to China, they were being forced into "a tricky balance."

"It is tough, to be honest," said Shiffrin, who has won more world titles (six) and world medals (11) than any other American skier, choosing her words carefully because of the sensitivity of the subject.

"The Olympics is big and it's something that you shoot for and you don't want to miss it, and you certainly don't want to be put in the position of having to choose between human rights, like morality, versus being able to do your job."

The International Olympic Committee (IOC) says that it raised concerns aired by rights groups with the Chinese government, and Shiffrin conceded that the IOC also finds itself having to make difficult decisions when selecting Olympic hosts.

"But it feels like there could be more consideration when you're hosting an event that's supposed to bring the world together and create hope, and peace, in a sense," she added.

"It could maybe be used in a better way... it's almost like a power that they have to decide where we go, and some places seem more fitting than others."