US stock futures were lower after chip darling Nvidia warned of a $5.5 bln charge linked to a U.S. export ban on some chips.

(Reuters) -Wall Street index futures dropped on Wednesday and chip darling Nvidia slumped after the company flagged steep charges from new U.S. curbs on chip exports to China, fuelling worries about the fallout of an escalating trade war.

U.S. stocks fell Wednesday after Nvidia warned new restrictions on exports to China will chisel billions of dollars off its results, while companies around the world said President Donald Trump's trade war is clouding forecasts for how they and the economy will do this year.