“We’re deeply concerned about the upcoming visit,” State Department spokesman Ned Price told reporters.

“We have no expectation that the PRC will grant the necessary access required to conduct a complete, unmanipulated assessment of the human rights environment in Xinjiang,” he said, using the acronym for the People’s Republic of China.

Price also criticised Bachelet, a former president of Chile, for not releasing a report on Xinjiang, where the US says Beijing is carrying out “genocide” against the mostly Muslim Uighurs and other Turkic-speaking people.

“Despite frequent assurances by her office that the report would be released in short order, it remains unavailable to us and we call on the high commissioner to release the report without delay and not to wait for the visit,” Price said.

He condemned her “continued silence in the face of indisputable evidence of atrocities in Xinjiang and other human rights violations and abuses throughout the PRC”.

“It is deeply concerning,” he said, as Bachelet should be a “leading voice on human rights”.

Witnesses and rights groups say more than one million people have been detained in indoctrination camps in Xinjiang that aim to destroy the Uighurs’ Islamic culture and forcibly integrate them into China’s Han majority.

Beijing denies genocide and says it is offering vocational training to reduce the allure of Islamist extremism.