Some prominent business allies of President Donald Trump are speaking out against the president’s tariffs, as the policy whipsaws markets and triggers recession warnings.

Billionaire financier Bill Ackman, who backed Trump’s 2024 campaign, on Monday slammed the tariffs as a “major policy error.”

“Business investment will grind to a halt, consumers will close their wallets and pocket books, and we will severely damage our reputation with the rest of the world that will take years and potentially decades to rehabilitate,” Ackman said in a post on X a day earlier, urging Trump to pause the policy rollout for 90 days.

Ackman warned the policy could bring about an “economic nuclear war.”

Tesla CEO Elon Musk, a top Trump adviser, said on Saturday that he wants a “zero-tariff situation” between the United States and Europe. The remarks came during a video conference interview with Matteo Salvini, Italy’s deputy prime minister.

Earlier that day, Musk sharply criticized tariff-advocate Peter Navarro, Trump’s senior counselor for trade and manufacturing.

“A PhD in Econ from Harvard is a bad thing, not a good thing,” Musk said about Navarro in a post on X.

The latest reversal came from JPMorgan Chase CEO Jaime Dimon, who released a letter to investors on Monday warning that Trump’s tariffs would raise prices and possibly tip the U.S. into a recession.

“Whether or not the menu of tariffs causes a recession remains in question, but it will slow down growth,” Dimon said.

As recently as January, however, Dimon voiced support for then-President-elect Trump’s tariff proposal and rebuked concerns about potential price increases.

“If it’s a little inflationary but it’s good for national security, so be it,” Dimon told CNBC. “I mean, get over it.”

Dimon, who did not endorse a candidate in the 2024 presidential election, praised Trump’s policies at the outset of last year.

“He was kind of right about NATO, kind of right on immigration. He grew the economy quite well. Trade tax reform worked. He was right about some of China,” Dimon told CNBC.

A market selloff on Monday extended losses that stretch back to Trump’s announcement of the far-reaching tariffs last week. The Dow suffered its worst week since 2020, and the Nasdaq ended last week in a bear market.

The new tariffs feature two key policies: A uniform 10% tariff for all imports and “reciprocal” tariffs imposed on roughly 60 nations that place duties on U.S. imports.

Trump has sent mixed signals about his willingness to negotiate with the target nations over the tariff levels.

“Countries from all over the World are talking to us,” Trump said Monday on Truth Social. “Tough but fair parameters are being set.”

Soon afterward, however, Trump threatened to slap an additional 50% tariff on China, unless the country withdraws 34% retaliatory tariffs announced last week.

Those retaliatory tariffs came in response to a 34% tariff announced by the U.S. days earlier, which came on top of 20% tariffs already imposed on China. The threatened 50% tariff would bring total U.S. tariffs on Chinese goods to 104%.

Over the weekend, billionaire investor Stanley Druckenmiller appeared to shift his posture toward Trump’s economic policies.

“I do not support tariffs exceeding 10%,” Druckenmiller said in a post on X on Sunday.

Less than three months earlier, Druckenmiller said CEOs were “giddy” about Trump’s election victory.

“We’re probably going from the most anti-business administration to the opposite,” Druckenmiller added.