July 7 (Reuters) - China's export restrictions on rare earths brought parts of the global auto supply chain to a halt and U.S. President Donald Trump to the negotiating table. But at home, they're a big headache for companies already struggling with a slow economy.

Low environmental standards helped China become the world’s low-cost producer of rare earths, but Beijing was also focused on helping the industry.

China’s rare earth export restrictions led to a 75% drop in magnet exports over two months, forcing automakers worldwide to halt production, Reuters reported. Beijing imposed the restrictions in April as a retaliatory measure for U.