In a social media post, Trump said China had begun notifying countries of its intent to impose broader export restrictions on rare earth-related materials. He expressed surprise at the move, citing what he described as recently "very good" relations with Beijing.The remarks triggered steep losses on Wall Street on Friday. The S&P 500 fell 2.7% -- its largest single-day drop since April. The Dow Jones Industrial Average dropped 1.9% and the tech-heavy Nasdaq slid 3.6%. Investors shifted to safe-haven assets, including gold and U.S. Treasury bonds, while the U.S. dollar weakened against a basket of major currencies.