(Reuters) - U.S. stock indexes opened sharply lower on Monday as investors shied away from risky assets on mounting concerns that the Trump administration's upcoming announcement of extensive tariff plans could hurt the global economy.

At 09:30 a.m. the Dow Jones Industrial Average fell 290.65 points, or 0.68%, to 41,293.25, the S&P 500 lost 56.93 points, or 1.01%, to 5,524.77, and the Nasdaq Composite lost 277.34 points, or 1.58%, to 17,039.68.