President Donald Trump’s plan to impose a 25% tariff on all imported aluminum could cost 100,000 American jobs, the CEO of one of the largest US aluminum makers warned on Tuesday.

Trump’s plan to expand aluminum tariffs spells higher costs for can and component makers, but aluminum producers say imports have held down prices.

Looming aluminum tariffs have put US makers of everything from cans to cars on edge. But as long as they’re willing to pay enough of a premium, the metal is likely to continue flowing across the northern border.