President Trump’s vow to impose tariffs on steel and aluminum next week rattled financial markets Thursday.

Stocks, which had already been down for the day, slipped further after the White House announced the planned tariffs. The Standard & Poor’s 500-stock index fell 1.2 percent to 2,682 Thursday afternoon, after falling roughly 2 percent earlier in the day.

Shares of automakers such as Ford and General Motors, large consumers of steel and aluminum, fell sharply, as the tariffs would raise the cost of raw materials.

“Historically, the automakers have to absorb these costs,” said Colin Langan, an analyst at UBS who covers automakers. “Consumers don’t adjust their price expectations based on higher steel prices.”