The Republican leaders of a US congressional commission on China urged President Donald Trump’s administration on Wednesday to broaden sanctions on Chinese officials over Beijing’s treatment of minority Muslims in the Xinjiang region.

In a letter on Wednesday, Senator Marco Rubio, chairman of the Congressional-Executive Commission on China, and Representative Chris Smith, the co-chairman, asked Secretary of Commerce Wilbur Ross to expand the list of Chinese entities barred from purchasing equipment that could be used for surveillance.

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“Given the national integration of China’s state security apparatus, we believe there should … be a presumption of denial for any sale of technology or equipment that would make a direct and significant contribution to the police surveillance and detection system (in the Xinjiang Uygur autonomous region),” Rubio and Smith said.

The US State Department on Tuesday expressed deep concern over China’s “worsening crackdown” on minority Muslims in the Xinjiang region, as the Trump administration considered sanctions against Chinese senior officials and companies linked to allegations of human rights abuses.