The slide started after Trump posted letters on his social media platform, Truth Social, that he says he sent to Japanese and Korean officials threatening them with 25% tariffs on goods being imported to the U.S. beginning Aug. 1. The countries can still reach a deal with his administration before then that could avoid those rates.

Later in the afternoon, the president posted additional letters he says he sent to Laos and Myanmar, which will face 40% tariffs starting on Aug. 1., and Kazakhstan and Malaysia, which will also see 25% duties. South Africa faces 30% tariffs. Trump also signed an executive order extending a 90-day “pause” on his tariffs to Aug. 1. It was originally set to expire Wednesday, July 9.

The announcement of the extension on the tariff pause was not enough to alleviate investors. Immediately following the president’s posts, shares of Alphabet, Apple, Honda, Nvidia, and Toyota all fell. The Nasdaq closed 0.92% lower, while the S&P 500 fell 0.79% and the Dow Jones Industrial Average shed 0.94%. The losses follow several indices hitting record highs last week.

An earlier threat from Trump also had investors worrying about tariffs.

“Any Country aligning themselves with the Anti-American policies of BRICS, will be charged an ADDITIONAL 10% Tariff. There will be no exceptions to this policy,” Trump wrote in a different post Sunday night, referring to the intergovernmental organization between countries including Brazil, China, Egypt, India, Saudi Arabia, and Russia, among others.

Monday’s tariff rates are the first of many other trade announcements the president is expected to make this week, according to White House press secretary Karoline Leavitt and Treasury Secretary Scott Bessent, who told CNBC Monday that “it’s going to be a busy couple of days.”

Only about 54% of imports from Japan and 46% of imports from South Korea would be exposed to the 25% tariffs, according to Capital Economics. That’s because the new rate would not apply to goods that fall under the president’s already-implemented product-specific tariffs, such as autos, as well as exemptions for electronics and pharmaceuticals.

“It’s telling that Trump has not (yet) released a letter threatening higher tariffs on the European Union, suggesting that he remains satisfied with how those bilateral trade talks are going,” writes By Paul Ashworth, Capital Economics’ chief North America economist. “From the European side, media reports suggest a draft framework deal is close to being agreed, which would allow time for more detailed negotiations.”

Meanwhile, Tesla stock fell almost 7% Monday, following CEO Elon Musk’s pronouncement that he planned to form a new political party after the passage of the Republican budget bill he opposed.

This article was updated to reflect the market close.