Dow futures drop 300 points as Street extends sell-off after Trump announced tariffs

U.S. stock index futures fell sharply on Friday as Wall Street braced for further losses.

Around 7:55 a.m. ET, Dow futures were indicating a drop of more than 250 points at the open. The Nasdaq and S&P 500 futures pointed to a negative open for their respective markets. The moves in U.S. futures came after Wall Street finished deep in the red during the previous trading session.

On Thursday, the Dow Jones industrial average tumbled 420 points, as investors reacted to news coming out of the central banking and political spheres.

Newly-appointed Fed Chair Jerome Powell spoke again Thursday to the Senate Committee on Banking about monetary policy and the state of the U.S. economy.

He said there were currently no "decisive" signs of wage inflation, just days after he stated that the central bank could raise interest rates three or more times during 2018 to prevent the U.S. economy from overheating.

Also Thursday, President Donald Trump said the U.S. would be imposing new tariffs on aluminum and steel. He is expected to set tariffs, as early as next week, of 25 percent on steel and 10 percent on aluminum, putting pressure on companies both domestic and international.

The move was roundly condemned, including by European Commission President Jean-Claude Juncker, who said it "can only aggravate matters." Consequently, markets overseas were trading deep in the red Friday.

But Trump stuck to his guns on Friday, tweeting: "When a country (USA) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win."