China has restricted the export of two metals used in computer chips and solar cells, stoking a trade dispute with Washington ahead of US Treasury Secretary Janet Yellen's visit to Beijing this week.
The controls on gallium and germanium are intended to "safeguard national security," the Ministry of Commerce said on Monday. Once the measure takes effect on August 1, an official permit will be required for export, he added without explaining what restrictions will apply.
Chinese President Xi Jinping's government is frustrated by US limits on its access to advanced chips and other technology for security reasons. But Beijing has been slow to retaliate, possibly to avoid hurting fledgling Chinese developers of processors, artificial intelligence and other technology.
Yellen is scheduled to arrive in China on Thursday as part of efforts by President Joe Biden's executive to revive relations that are at their worst in decades over disputes over technology, Chinese military expansion, human rights and other contentious issues.
China is the world's top supplier of gallium and germanium, which are produced in small quantities but are needed to make chips used in cell phones, and other products such as solar panels and military technology.
The United States gets almost half its supply of both metals directly from China, according to the US Geological Survey. China last year exported about 23 metric tons (25 tons) of gallium and produces about 600 metric tons (660 tons) of germanium.
