China has begun restricting exports of critical minerals used by U.S. and European defense contractors, according to an Aug. 4 Wall Street Journal report. The paper said the tighter curbs, which cover rare earths and other key inputs for ammunition, missiles and jet fighters, are slowing deliveries and undermining already stretched military supply chains. Executives quoted in the report said the shortages are delaying production schedules and compelling companies to scour alternative sources worldwide. The export squeeze adds to broader trade and security tensions between Beijing and Western capitals, which have been seeking to reduce dependence on Chinese raw materials.