Stocks fell on Thursday after President Donald Trump said the U.S. will implement tariffs on steel and aluminum imports next week.

The Dow Jones industrial average traded 550 points lower after rising more than 150 points earlier in the day. The S&P 500 declined 1.8 percent, with tech as the worst-performing sector. The Nasdaq composite fell 1.9 percent and broke below its 50-day moving average, a key technical level.

The U.S. will set tariffs of 25 percent for steel and 10 percent for aluminum, the president said. It is unclear whether they will apply to all imports or only metals from certain countries.

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