PATRICK T. FALLON/AFP via Getty Images Bill Ackman said President Donald Trump's call for a one-year cap on credit card interest was a "mistake." The hedge fund billionaire said a rate cap could lead to millions having credit cards canceled. Trump on Friday called for a 10% cap on credit card interest for one year. Bill Ackman did not mince words when giving his opinion of President Donald Trump's call for a temporary cap on credit card rates. In a since-deleted X post, the hedge fund billionaire said late on Friday that Trump's call for a 10% cap on credit card interest for one year was a "mistake" that could lead to millions having their cards canceled. "This is a mistake President," Ackman wrote. "Without being able to charge rates adequate enough to cover losses and to earn an adequate return on equity, credit card lenders will cancel cards for millions of consumers who will have to turn to loan sharks for credit at rates higher than and on terms inferior to what they previously paid." Trump had taken to Truth Social earlier on Friday in a fresh effort to address the hot political issue of "affordability," saying his administration intended to target lenders charging interest rates of "20 to 30%." "Please be informed that we will no longer let the American Public be 'ripped off,'" he said. "Effective January 20, 2026, I, as President of the United States, am calling for a one year cap on Credit Card Interest Rates of 10%." Such a cap would likely require authorization by Congress. It is unclear what moves the president could make to bypass this. In a new post on Saturday, Ackman, the CEO of Pershing Square Capital Management, said Trump's "goal of reducing credit card interest rates" was a "worthy and important one," but he reiterated his concerns over a 10% cap. "I have no investments in the credit card space so I am not the expert, but the market for credit cards appears highly competitive," Ackman continued. "The best way to bring down rates would be to make it more competitive by making the regulatory regime more conducive to new entrants and new technologies." Trump, who pledged to "immediately bring prices down" in office, has recently honed in on the topic of affordability. New York City mayor Zohran Mamdani swept to victory in November after running a campaign focused on voters' cost-of-living concerns. Business Insider has contacted the White House for comment. Read the original article on Business Insider