AsianFin -- American and other Western officials are expressing concern that a key Vietnamese tungsten mine and refinery could fall under Chinese control, potentially limiting access to a major source of the critical mineral outside China, Reuters reported on Wednesday, citing sources familiar with the matter.

Rising U.S.-China trade tensions have prompted Beijing, the world’s dominant tungsten supplier, to restrict exports of the metal and other critical minerals in response to U.S. tariff policies.

The Nui Phao complex in northern Vietnam, owned by Masan High-Tech Materials—a subsidiary of the Masan conglomerate—has reportedly been put up for sale, according to five sources.

Two Chinese companies have reportedly approached foreign firms, seeking to use them as proxies to bid for a stake in the Nui Phao operation, one source familiar with the discussions said.