US stocks today: S&P 500 and Nasdaq open lower as Iran tensions jolt sentiment, chip stocks slide

US stock markets opened lower on Tuesday as escalating Iran tensions weighed on investor sentiment and chip stocks declined. The S&P 500 fell 27.9 points or 0.37 percent to 7,547.53, while the Nasdaq Composite dropped 193.3 points or 0.74 percent to 26,088.31 at the opening bell. The Dow Jones Industrial Average was the only gainer, rising 39.5 points or 0.08 percent to 52,676.53, as global risk appetite soured.