WASHINGTON—President-elect Donald Trump pledged that soon after taking office he will slap steep tariffs on Mexico and Canada, two of America’s closest allies, as well as China, the clearest indication since his election victory that he plans to follow through on the tough campaign rhetoric that helped propel him to the White House.

The U.S. dollar rose broadly against major rivals on Tuesday after President-elect Donald Trump said he would sign an executive order imposing a 25% tariff on all products coming in to the United States from Mexico and Canada.

He said the countries weren't doing enough to control the flow of illegal drugs, especially fentanyl, and migrants across the border.