GENEVA — As China prepared to defend its record before the United Nations Human Rights Council, the United States on Wednesday led Western governments, academic experts and human rights supporters in challenging Beijing over its mass detention of Muslims in the western region of Xinjiang.

China’s oppression of religious and ethnic minorities is well known. “What’s new is the breadth of the repression and how the Chinese government is using breakthroughs in technology to increase its effectiveness,” Kelley Currie, a senior United States diplomat, told a meeting on the sidelines of the council in Geneva.

The United States would consider targeted measures against Xinjiang officials to promote accountability for violations there, said Ms. Currie, who serves with the State Department’s Office of Global Criminal Justice. She urged China to reverse its policies and allow access to the region by United Nations experts.

The United States withdrew from the human rights council last year, accusing it of having an anti-Israeli bias and serving as a platform for some of the world’s worst rights abusers, but it has since pulled back from complete disengagement.