Trump is breaking from his “America First” trade agenda and feuding with some of his most loyal supporters in a fight over U.S. beef prices.

Trump has centered his economic agenda on reducing the U.S.’s reliance on cheaper foreign products and boosting domestic production of goods and food. But his plan to boost imports of Argentinian beef while urging American suppliers to lower their prices marks a sharp departure from his platform.

The dispute is threatening Trump’s long-standing support from agriculture groups and workers, who stood by the president during his first term despite the backlash they faced from his trade agenda.