The legislation, proposed by the Congressional-Executive Commission on China, would also support an existing push for sanctions against Xinjiang Communist Party chief Chen Quanguo and other officials under the Magnitsky Act, which would prevent Chen from entering the US and freeze any assets he has in US banks.

Other sanctions raised for consideration by the proposed act include a ban on sales or provision of US-made goods or services to Xinjiang state agents and the barring of certain Chinese entities – including the Xinjiang police bureau – from purchasing US-made equipment that could be used for surveillance.

The bipartisan congressional commission monitors human rights and the rule of law in China.

FBI chief tells US Congress that China poses bigger security threat than Russia

Chinese authorities have denied that the internment camps exist but say petty criminals are sent to “vocational training centres.” On Tuesday, the Xinjiang government revised legislation to officially permit the use of “education and training centres” to reform “people influenced by extremism”.

A new clause directs the centres to teach the Mandarin language, occupational and legal education, as well as “ideological education, psychological rehabilitation and behaviour correction”.

Australian scholar James Leibold called the move a “retrospective justification” for mass detentions.

“It’s a new form of re-education that’s unprecedented and doesn’t really have a legal basis, and I see them scrambling to try to create a legal basis for this policy,” said Leibold, an expert on Chinese ethnic policies at Melbourne’s La Trobe University.

Maya Wang, senior China researcher at Human Rights Watch, said “no tweaks in national or regional rules” could change the nature of the camps.

“Without due process, Xinjiang’s political education centres remain arbitrary and abusive,” she said.

The ruling Communist Party says heightened security is necessary to combat extremism in Xinjiang.

The measures proposed by US lawmakers come as US-Chinese relations have deteriorated amid a growing tariff dispute over American complaints about Beijing’s technology policy.

Last week, US Vice-President Mike Pence accused Beijing of trying to influence the outcome of the November midterm elections. The Chinese foreign ministry rejected that as “groundlessly accusing and slandering China”.

Beijing has spent decades trying to suppress pro-independence sentiment in Xinjiang, fuelled in part by frustration about an influx of migrants from China’s Han majority. Authorities say extremists there have ties to foreign terror groups.

The congressional measure calls for the creation of a State Department post to coordinate financial and diplomatic responses, a database for US residents to provide details about missing family members and an expedited asylum process for the affected minority groups.

China changes law to recognise 're-education camps' in Xinjiang

The congressional commission also warned in an annual report on Wednesday of the “long arm” of an “ascendant and increasingly aggressive” China.

The 300-page report describes a “downward trajectory” on human rights since Xi took power in 2012. It says the ruling party is “trying to redefine” human rights and “basic human dignity”.

“China’s authoritarianism at home directly threatens our freedoms as well as our most deeply held values and national interests,” said a statement by US Republican Senator Marco Rubio and Representative Chris Smith.

The European Union expressed similar concern about Xinjiang last week.

The EU is “deeply concerned by credible reports pointing to a serious deterioration” of human rights, said the 28-nation bloc’s chief foreign policy official, Federica Mogherini, calling on all countries to carefully consider asylum requests.

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Omir Bekali, who was profiled by Associated Press in May, is named in the proposed legislation as among those who have testified to the indoctrination, humiliation and indefinite detention of internees.

Detainees were ordered to chant “Thank the party! Thank the motherland!” before meals, according to Bekali, a Chinese-born citizen of the central Asian nation of Kazakhstan.

The congressional commission is also seeking information from the FBI on Chinese activity on US soil. American citizens, Chinese students and other US residents say they have been harassed over Xinjiang, the commission said in a letter to FBI Director Christopher Wray.

Uygurs in Istanbul, Turkey, told AP this year that Chinese authorities asked them to spy on fellow Uygurs abroad in exchange for information about family members in Xinjiang.