WASHINGTON -- Brushing aside stern warnings from from ally nations, U.S. companies and lawmakers in his own party, President Trump imposed substantial tariffs Thursday on steel and aluminum imports from across the globe.
His order included an indefinite but conditional exemption for Canada and Mexico.
The order marked the first time in more than three decades that a U.S. president has invoked national security as the basis for ordering such trade restrictions.
The protectionist move is almost certain to be contested at the World Trade Organization and met with retaliatory measures from other nations, risking a trade war.
And the sloppy rollout, lack of details and uncertain process that lay ahead could mean that the tariff plan -- like so many other Trump programs -- finds itself tied up in legal challenges or congressional roadblocks.
The new tariffs -- 25 percent on imported steel and 10 percent on aluminum -- will take effect in 15 days.
Trump signed the orders Thursday afternoon in the White House, with steel and aluminum workers in attendance.
Earlier in the day, Trump indicated that the tariff waiver for Canada and Mexico could be rescinded or made permanent depending on the outcome of ongoing renegotiation of the North American Free Trade Agreement.
The Trump administration is separately trying to rewrite NAFTA, but talks have progressed slowly. Both Mexico and Canada have balked at Trump's move to link the NAFTA renegotiations with the impending tariffs.
While only Canada and Mexico were specifically excluded from the tariff orders, Trump and his aides made it clear that other nations also could be exempted from the new duties.