TechnologyOpens a New Window.
 shares Tuesday helped drag down major indexes of U.S. stocksOpens a New Window., already struggling on concerns over tensions with Iran and comments by the head of the Federal ReserveOpens a New Window..

And in another sign of weakening investor sentiment, the yield on the benchmark 10-year Treasury fell below 2 percent. Bond yields, or interest rates, move in the opposite direction of bond prices.

The latest U.S. sanctions by President TrumpOpens a New Window. on IranOpens a New Window. drew a sharp rebuke from the Islamic Republic on Tuesday, with Iranian President Hassan Rouhani calling the economic crackdown “outrageous and idiotic.”

Tensions between Tehran and Washington heightened last week after an Iranian missile shot down an unmanned U.S. spy drone over the Strait of Hormuz.

Investors are looking toward the upcoming U.S.-China trade talksOpens a New Window. to help reduce tensions of a trade war that is damaging the global economy.

Later this week, Trump and Chinese President Xi Jinping are expected to meet at the G-20 summit in Japan.

Federal Reserve Chairman Jerome Powell seemed to take a subtle swipe at Trump during a speech on Tuesday in New York, warning of “short-term political pressure” that can damage the U.S. central bank’s independence.