Sen. Tom Cotton on Wednesday expressed opposition to President Trump’s proposal to enact steep tariffs on imported steel and aluminum.

The Arkansas Republican is among Trump’s most dependable partners on Capitol Hill, aligning himself in particular with the president on immigration issues. But he disagrees with Trump’s plan to hit almost all countries — ally and adversary alike — with steel and aluminum tariffs, warning that it could harm the U.S. economy and raise the price of consumer staples.