Stocks closed markedly lower in the first trading session since President Donald Trump announced a new 15% tariff on most imported goods, intensifying his effort to impose levies that were struck down by the Supreme Court.

The Dow Jones Industrial Average fell 820 points, or 1.6%, while the S&P 500 dropped 1%. The tech-heavy Nasdaq declined 1.1%.

Some tech stocks fell sharply as advances in artificial intelligence continued to reverberate through the markets, putting further drag on the major stock indexes. Shares of International Business Machines (IBM) closed down more than 13%.

Cryptocurrency prices also tumbled on Monday. The price of bitcoin fell 4.3%, putting it at about $64,450, its lowest level since Feb. 3.

Gold prices jumped to their highest level in three weeks as investors sought the safe-heaven asset amid heightened uncertainty.

In a social media post on Monday, Trump reiterated his criticism of the Supreme Court.

The Supreme Court, Trump said, “accidentally and unwittingly gave me, as President of the United States, far more powers and strength than I had prior.”

Trump retains the power to levy a 15% tariff for up to 150 days under the Trade Act of 1974, which allows the president to address trade disparities with other countries.

Hours after the Supreme Court ruling on Friday, Trump said he would sign an executive order enacting a new 10% “global tariff,” invoking authority under Section 122. On Saturday, Trump escalated the tariff to 15%.

Trump vowed to initiate investigations as part of an effort to impose additional tariffs over the coming months.

“It’s a little longer process,” Trump said at the White House on Friday. “I tried to make things simple but they wouldn’t let us do that.”

The high court ruled that the International Emergency Economic Powers Act (IEPPA) does not authorize Trump to impose levies, nullifying a major swathe of country-specific tariffs issued by the president on “Liberation Day,” as well as a 10% tariff placed on all imports and a host of other measures.

Some tariffs issued by Trump will be unaffected by Friday’s ruling, including a 50% levy on all steel and aluminum products.