Republican lawmakers stepped up calls on Tuesday for President Donald Trump to pull back from proposed tariffs on steel and aluminum imports as Senate Majority Leader Mitch McConnell added to an avalanche of criticism of the measures, saying they risked igniting a trade war and damaging the U.S. economy.

McConnell's comments came after House of Representatives Speaker Paul Ryan criticized the proposed 25 percent duty on steel and 10 percent on aluminum as too broad. Although the measure is designed to hit China, its main impact will be on U.S. allies like Canada.

The White House has said the measures will protect industries and jobs from unfair competition and that across-the- board tariffs are needed because countries like China use third countries for shipping steel to the United States, disguising its origin.