President Trump defied opposition from his own party and protests from overseas as he signed orders on Thursday imposing stiff and sweeping new tariffs on imported steel and aluminum. But he sought to soften the impact on the United States’ closest allies with a more flexible plan than originally envisioned.
After a week of furious lobbying and a burst of last-minute internal debates and confusion, Mr. Trump agreed to exempt, for now, Canada and Mexico, and held out the possibility of later excluding allies like Australia. But foreign leaders warned of a trade war that could escalate to other industries and take aim at American goods.