WASHINGTON (Reuters) - A bipartisan group of U.S. lawmakers on Wednesday faulted the Trump administration for failing so far to impose sanctions over China’s alleged human rights abuses against its Muslim minority and called for punitive measures against a senior Communist Party official and Chinese companies.

FILE PHOTO: Workers walk by the perimeter fence of what is officially known as a vocational skills education centre in Dabancheng in Xinjiang Uighur Autonomous Region, China September 4, 2018. REUTERS/Thomas Peter/File Photo

A letter to President Donald Trump’s top advisers signed by more than 40 lawmakers said China’s actions in its western region of Xinjiang “may constitute crimes against humanity” and urged tighter U.S. export controls to ensure that U.S. companies are not assisting the Chinese government’s crackdown there, either directly or indirectly.

It also asked the United States to strengthen financial disclosure requirements to alert American investors about the presence in U.S. capital markets of Chinese companies that are “complicit in human rights abuses.” The letter specifically cited Hikvision and Dahua Technology, which produce audio-visual equipment that can be used for surveillance.

China faces growing condemnation from Western capitals and rights groups for setting up facilities that U.N. experts describe as mass detention centers holding more than 1 million ethnic Uighurs and other Muslims.

Beijing has said its measures in Xinjiang, which are also reported to include widespread surveillance of the population, are aimed at stemming the threat of Islamist militancy. The facilities or camps that have opened are vocational training centers, the government has said.

The letter, which was sent to Secretary of State Mike Pompeo, Treasury Secretary Steven Mnuchin and Commerce Secretary Wilbur Ross, urged them to swiftly slap sanctions on Xinjiang’s Communist Party chief Chen Quanguo, a member of the Chinese leadership’s powerful politburo, and other Chinese officials “complicit in gross violations of human rights.”

The Trump administration has been weighing sanctions against Chinese officials, including Chen, since late last year, and though it has ramped up criticism it has held off on imposing the measures. China has warned that it would retaliate “in proportion” against any U.S. sanctions.

“We are disappointed with the administration’s failure so far to impose any sanctions related to the ongoing systemic and egregious human rights abuses in Xinjiang,” the lawmakers said. “While the strong rhetoric condemning the Chinese government’s actions (in Xinjiang) from Vice President Pence and others is certainly welcomed, words alone are not enough.”

The group of signatories was led by U.S. Senator Marco Rubio and U.S. Representative Chris Smith on the Republican side and Senator Bob Menendez and Representative James McGovern on the Democratic side.

They called on the Trump administration to apply sanctions under the Global Magnitsky Act. The federal law allows the U.S. government to target human rights violators around the world with freezes on any U.S. assets, U.S. travel bans and prohibitions on Americans doing business with them.