"I disagree with this action and fear its unintended consequences," Paul Ryan said in a statement shortly after Trump signed two executive orders imposing broad steel and aluminum tariffs.
Ryan said he and those who share his concerns will "continue to urge the administration to narrow this policy so that it is focused only on those countries and practices that violate trade law."
Ryan's statement echoed the position of at least 107 other Republican members of Congress, who signed a letter Wednesday urging Trump to "reconsider the idea of broad tariffs to avoid unintended negative consequences to the U.S. economy and its workers."
Like the letter, which was signed by House Ways and Means Committee Chairman Kevin Brady, Ryan's statement agreed that "targeted enforcement" against "bad trade practices by nations like China" are preferable to a global tariff on steel and aluminum imports.
Sen. Jeff Flake, R-Ariz., also came out against the tariffs and said he would introduce legislation intended to nullify the president's move.
"Trade wars are not won, they are only lost," said Flake, a frequent Trump critic who has decided not to pursue reelection. "Congress cannot be complicit as the administration courts economic disaster."
Flake's bill, however, is likely to be seen as a symbolic gesture.
The tariffs impose penalties of 25 percent on steel imports and 10 percent on aluminum.
"A strong steel and aluminum industry are vital to our national security," Trump said before signing the orders. "You don't have steel, you don't have a country."
Trump used a report from Commerce Secretary Wilbur Ross outlining national security threats as a basis for justifying the tariffs.
But Ryan disagreed, saying: "Our economy and our national security are strengthened by fostering free trade with our allies and promoting the rule of law."