US stocks tumbled Friday after President Donald Trump threatened a massive increase in tariffs on Chinese imports. The threat is retaliation for China's new restrictions on rare earth exports — materials vital for AI, semiconductors, defense, and high-tech industries. The S&P 500 fell 1.7 percent, the Nasdaq dropped 2.5 percent, and the Dow Jones lost more than 500 points, as investors reacted to escalating trade tensions and uncertainty over US-China relations. 'Some very strange things are happening in China,' Trump wrote on Truth Social. 'They are becoming very hostile, and sending letters to countries throughout the world, that they want...