The United Nations High Commissioner for Human Rights said on Thursday that she is still aiming to release a long-anticipated report on China's treatment of its Uyghur minority in Xinjiang by the end of her four-year mandate next week.

Michelle Bachelet, a former president of Chile, has faced severe criticism from civil society for being too soft on China during a visit earlier this year and has since said she will refrain from seeking a second term for personal reasons.

The report has been in the works for three years and promised for months but has not been published for unclear reasons.

"We are trying very hard to do what I promised," Michelle Bachelet said at a press briefing in Geneva, referring to a pledge to release it before the end of her term on Aug. 31.

Asked to elaborate on why it has not been released, she said she needed time to integrate new information from her May visit.

Rights groups accuse Beijing of abuses against Uyghurs living in the western region of Xinjiang, including the mass use of forced labour in internment camps. China has vigorously denied allegations of state persecution of Uyghurs, a mainly Muslim ethnic minority that numbers around 10 million people.

Reuters reported last month that China had asked Bachelet to bury the report, according to a Chinese letter that was confirmed by diplomats from countries who received it.

Bachelet confirmed on Thursday having received that letter which she said was signed by about 40 other states, adding that her office would not respond to such pressure.