U.S. stocks came under pressure at the opening bell after President Donald Trump threatened to impose tariffs on Mexican imports. The S&P 500 SPX, +0.29% fell 0.8% to 2,766. The Dow Jones Industrial Average DJIA, +0.19% shed 253 points , or 1%, to 24,917. The Nasdaq Composite COMP, +0.36% slipped 1.2% to 2,475. Equities slipped following Trump's announcement that the U.S. would impose a 5% tariff on all Mexican imports, which would gradually increase every month unless that country halted the flow of illegal immigrants into the U.S. The tariffs would progressively increase until they hit 25% by Oct. 1. Reports that China was also contemplating different retaliatory measures also sparked further investor jitters. Shares of automakers with supply chains dependent on trade across the U.S.-Mexico border slumped on Friday. Shares of General Motors Co. GM, -0.78% fell 4.8%, while Ford Motor Co. shares F, +0.30% fell 2.9%.