JPMorgan Chase CEO Jamie Dimon sounded the alarm on President Donald Trump’s tariffs in his annual letter to shareholders, warning the trade policy will likely spike inflation and is sure to slow down growth.

Dimon said “at least until recently” the U.S. economy was proving resilient “despite the unsettling landscape.” That changed when Trump announced sweeping tariffs on almost every American trading partner, which sent stocks to their worst week since the height of the COVID-19 pandemic.

“The recent tariffs will likely increase inflation and are causing many to consider a greater probability of a recession,” Dimon wrote.

“And even with the recent decline in market values, prices remain relatively high,” he continued. “These significant and somewhat unprecedented forces cause us to remain very cautious.”

Dimon explained he started writing the letter amid a weakening U.S. economy, adding “that was before the recent tariff announcement.” He told shareholders to not only expect rising prices on imported and domestic goods, but to prepare for a bevy of uncertainty. He cited “the potential retaliatory actions, including on services, by other countries, the effect on confidence, the impact on investments and capital flows, the effect on corporate profits and the possible effect on the U.S. dollar.”

The JPMorgan exec isn’t alone in his concerns. Billionaire hedge fund manager and Trump super fan Bill Ackman wrote a lengthy post Sunday urging the president to hit pause on the trade war or risk crashing the economy. “We are heading for a self-induced, economic nuclear winter, and we should start hunkering down,” Ackman said.

Stock futures early Monday morning showed the S&P 500 poised to be almost 3% lower. Monday has the potential to be a truly historic day in the stock market — and not in a good way. If the benchmark index were to lose more than 4% in value, it would be the third consecutive trading day it has posted declines of more than 4%. That would be the first time the S&P 500 has suffered three consecutive drops of more than 4% in almost a century, since the 1929 stock market crash that marked the onset of the Great Depression.

Futures tied to the Nasdaq were off 2.9% and Dow Jones Industrial Average Futures fell 2.5%.