The S&P 500 and Nasdaq indexes fell as a rebound in technology shares faded and President Donald Trump said the US must react to Iran's shooting down of a US helicopter.
Trump wrote in a social media post on Tuesday that Iran had shot down the US Apache helicopter that was patrolling the Strait of Hormuz overnight, and vowed to respond, which added to doubts about prospects for a truce in the Middle East war.
The Cboe Volatility Index hit its highest level since April 7 during the session as stocks sold off.
