Tariff Threats Show Trump’s Commitment to Upending Global Trade

President-elect Donald J. Trump’s threats to impose damaging tariffs on Canada, Mexico and China may ultimately be an opening wager to try to use the power of the American market to persuade other countries to stem a flow of drugs and migrants across U.S. borders.

But even if the threat to impose vast tariffs on some of the world’s largest economies is a negotiating tactic, it is also a gambit that has immediate real-world consequences.

Before Mr. Trump even sets foot in the Oval Office, his threat to put tariffs on America’s three largest trading partners on his first day in office was reverberating around the world, shocking international businesses, rocking diplomatic relationships and calling into question two big trade deals that Mr. Trump negotiated during his first term.

Mr. Trump’s pronouncement late Monday that he would impose a 25 percent tariff on all goods from Canada and Mexico and a 10 percent tariff on products from China was immediately denounced by business groups, who said such a move would cause grave economic harm. Foreign officials rushed to reassure the incoming Trump administration that they had been working to stop drugs and migrants from coming into the United States — while warning that they were also ready to turn around and impose their own tariffs on American exports.

Mr. Trump’s threats may have been intended to silence investors and economists who have recently questioned whether the president-elect would go through with imposing the big levies he promised while campaigning. In the run-up to the election, Mr. Trump pledged to put a 60 percent tariff on goods from China and a tax of at least 10 percent on all other imports. Such a move could ignite a global trade war, slowing economies