New Delhi, Feb. 27 -- IN 1973 a club of Arab petrostates held the world to ransom by halting crude-oil exports to countries they accused of supporting Israel. Petrol prices soared; Western economies buckled. Today the danger is that China will use its grip on other natural resources to achieve its aims, such as seizing Taiwan. It has already shown its power by choking off exports of rare-earth metals last year. That is why America is staging its biggest intervention in commodity markets in decades.

The battleground is the supply of "critical" metals, a group of minerals vital to making military, electrical and computing infrastructure-everything modern economies need to be safe, high-tech and green. China supplies most of these: it mines...