China mines about 70% of the world's rare earths but has a virtual monopoly on refining and processing. Even if the pace of export approvals quickens as Trump suggested, the new system gives Beijing unprecedented glimpses of how companies in a supply chain deploy the rare earths it processes, European and U.S. executives have warned.

A key component of the Biden administration’s China strategy was a focus on bolstering ties with allies and partners to counter Beijing’s growing global footprint. Trump’s approach to China — and the rest of the world — hinges on tariffs and trade. How effective is that?