President-elect Donald Trump on Monday promised massive hikes in tariffs on goods coming from Mexico, Canada and China starting on the first day of his administration, a policy that could sharply increase costs for American businesses and consumers.

In a post on Truth Social, Mr. Trump mentioned a caravan of migrants making its way to the United States from Mexico, and said he would use an executive order to levy a 25 percent tariff on goods from Canada and Mexico until drugs and migrants stopped coming over the border.