Major stock indexes plunged Thursday afternoon following President Trump’s announcement that he was imposing a 25% tariff on imported steel and 10% on aluminum.

Stocks fell on Thursday after President Donald Trump said the United States. 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%, with tech as the worst-performing sector. The Nasdaq composite fell 1.9% and broke below its 50-day moving average, a key technical level.

It was not immediately clear whether Trump would exempt some countries from the tariffs, as his national security advisers have urged him to do to avoid hurting key U.S. allies.

Continuously declining oil prices, weak economic indicators, international investment uncertainty and disappointing quarterly earnings reports were all believed to have contributed to a morning drop that has become routine for traders in the new year. 

"What's been allowed to go on for decades is disgraceful. It's disgraceful," Trump told a group of steel and aluminum executives at the White House's Cabinet Room. "You will have protection for the first time in a long while and you're going to regrow your industries." 

Increased foreign production, especially by China, has driven down prices and hurt U.S. producers, creating a situation the Commerce Department calls a national security threat.

Any action to impose tariffs is likely to escalate simmering tensions with China and other U.S. trading partners. Critics of such a move fear that other countries will retaliate or use national security as a pretext to impose trade penalties of their own. 

Also, the Cboe Volatility Index (VIX) also soared by more than 20%.