Bill Ackman has a warning for President Donald Trump: Hit pause on the trade war or risk crashing the economy.

“The country is 100% behind the president on fixing a global system of tariffs that has disadvantaged the country,” Ackman, the billionaire CEO of Pershing Square Capital Management, said in a lengthy post Sunday on X. “But, business is a confidence game and confidence depends on trust.”

“By placing massive and disproportionate tariffs on our friends and our enemies alike and thereby launching a global economic war against the whole world at once, we are in the process of destroying confidence in our country as a trading partner, as a place to do business, and as a market to invest capital,” Ackman went on. “The president has an opportunity to call a 90-day time out, negotiate and resolve unfair asymmetric tariff deals, and induce trillions of dollars of new investment in our country.”