U.S. Allies Around the World Steel for Trump Tariff Tussle

President Donald Trump’s planned tariffs on steel and aluminum put U.S. allies around the globe in a tough spot Friday, driving down stock prices and generating warnings of a possible international trade war.

Allies in Asia and Europe lobbied for a change of heart and took issue with Mr. Trump’s invocation of a little-used Cold War-era law that gives presidents broad discretion to curb imports deemed a threat to national security.