A senior manager at a company that churns out metals routinely used in U.S. smart bombs pauses in mid-sentence when his phone rings: a Wall Street stockbroker looking for information. He makes a note to have an assistant call back -- someone who is fluent in English, not just Chinese.

“It’s a seller’s market now,” says Bai Baosheng, 43, puffing a cigarette in his office in Baotou, China, where his company sells bags of powder containing a metallic element known as neodymium, vital in tiny magnets that direct the fins of bombs dropped by U.S. Air Force jets in Afghanistan.

A generation after Chinese leader Deng Xiaoping made mastering neodymium and 16 other elements known as rare earths a priority, China dominates the market, with far-reaching effects ranging from global trade friction to U.S. job losses and threats to national security.

The U.S. handed its main economic rival power to dictate access to these building blocks of modern weapons by ceding control of prices and supply, according to dozens of interviews with industry executives, congressional leaders and policy experts. China in July reduced rare-earth export quotas for the rest of the year by 72 percent, sending prices up more than sixfold for some elements.