And while China and the United States have promised a truce over rare earth minerals, the wheels of advanced technology are beginning to slow. Without yttrium, the production of aircraft engines, high-efficiency turbines, advanced energy systems, and semiconductors would immediately slow down. China's RoleThe problem is that, as with several other resources, China controls almost the entire global yttrium supply chain. According to US data, the United States imports 100 percent of its yttrium needs, 93 percent of which comes directly from China. When Beijing decided to introduce export restrictions as a response to US tariffs, the entire international supply structure began to falter.