The US has ordered border officials to block shipments of clothing, computer parts and other products made at select locations in China's Xinjiang region.
The move is the latest by the Trump administration to put pressure on China over its treatment of Xinjiang's Uighur Muslims.
The US said the sites use forced or prison labour.
China is believed to have detained more than one million people from Xinjiang, citing security risks.
It has said its programmes, which have included transferring detainees to manufacturing sites, provide job training and education and are necessary to combat terrorist and separatist threats.
Washington and Beijing have repeatedly clashed over the practices, with the US accusing the country of human rights abuses.
The orders on Monday "send a clear message to the international community that we will not tolerate the illicit, inhumane, and exploitative practices of forced labour in US supply chains," Mark A. Morgan, acting commissioner of US Customers and Border Protection agency, said.
"The Trump administration will not stand idly by and allow foreign companies to subject vulnerable workers to forced labour while harming American businesses that respect human rights and the rule of law."
The orders the US announced on Monday fall short of the region-wide ban that it had considered. Officials said, however, they were still exploring that possibility.
"Because of its unique nature, being, applying to a region as opposed to a company or a facility, we are giving that more legal analysis," Department of Homeland Security acting secretary Kenneth Cuccinelli said.
"We want to make sure that once we proceed that it will stick, so to speak."
China produces about 20% of the world's cotton with most of it coming from Xinjiang. The region is also a major source of petrochemicals and other goods that feed into Chinese factories.
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