The US has blacklisted seven Chinese groups it accuses of building supercomputers to help its military.It is the first move by the Biden administration to make it harder for China to obtain US technology.
On Thursday, three companies and four branches of China's National Supercomputing Center were added to the US blacklist.
This bars American companies from exporting technology to the groups without proper approval.
The US commerce department said the groups were involved in building supercomputers used by Chinese "military actors" and facilitating programmes to develop weapons of mass destruction.
The sanctioned groups are leading China's supercomputing development and are key players in Beijing's plan for chip self-sufficiency.