“The message was, this is a supply chain and we control your supply chain,” said Clint Cox, president of the Anchor House, a rare-earths consulting firm in Evanston, Ill.

The dilemma for Beijing lies in whether to jeopardize its central role in global supply chains by halting exports of crucial components to the West. Trade hawks in the Trump administration have been quietly expressing hope that China will do just that. They see such an interruption as the best way to persuade global companies to shift manufacturing permanently out of China to the United States or to American allies, a long-term goal known as decoupling in trade circles.

A Chinese export embargo would have other drawbacks. For example, American oil refineries depend on lanthanum, which is the cheapest and most easily produced of the 17 rare-earth elements, as a catalyst to refine crude oil. But lanthanum is mined in bulk in Australia and in the United States as well as in China.

Oil companies in the United States keep several months of catalysts in stockpiles, said Dudley Kingsnorth, a professor specializing in rare earths at the Western Australian School of Mines in Perth. The United States could import more gasoline and diesel from refineries elsewhere if needed, although at a greater cost.

https://www.nytimes.com/2019/05/23/business/china-us-trade-war-rare-earths.html