GUANGZHOU, China — The U.S. government has reportedly imposed restrictions on exports to SMIC, China’s biggest chip manufacturer, a move that threatens Beijing’s push to become more self-reliant in one of the most critical areas of technology.

Suppliers for certain equipment to SMIC will need to apply for an export license, according to a letter sent to companies by the U.S. Department of Commerce, reported by several media outlets. The commerce department claims there is “unacceptable risk” that equipment sold to SMIC may be diverted to “military end use.”