The Dow Jones industrial average sank 250 points Thursday morning after President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE announced that he would impose steel and aluminum tariffs on Canada, Mexico and the European Union.

The S&P 500 dropped 0.5 percent.

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Both Mexico and the EU announced retaliatory tariffs in response to Trump's announcement, with Mexico promising to slap taxes on American steel products, pork and various agriculture and the EU imposing taxes on imported American bourbon, jeans and motorcycles, among other products.

U.S. steel stocks, however, got a boost from the protectionist measures, with stocks in companies such as U.S. Steel spiking as much as 7 percent in early trading.

Commerce Secretary Wilbur Ross Wilbur Louis RossTrump admin asks Supreme Court to fast-track excluding people in U.S. illegally from census Trump 'very happy' to allow TikTok to operate in US if security concerns resolved TikTok, WeChat to be banned Sunday from US app stores MORE brushed off the market reaction.

"A 170-[point decline] is not very cataclysmic in any event," he told CNBC earlier Thursday, before the market further declined.

"Naturally, if the market, to the degree it was surprised, it'll have to adjust to that. But markets adjust to facts," he added.

Markets have seen extreme swings in recent months amid fears of an overheated market and uncertainty regarding American trade policy, interest rates and European politics.

Trump is also considering hefty tariffs on automobiles and a slew of Chinese imports and struggling to renegotiate the North America Free Trade Agreement with Canada and Mexico.