President Donald Trump on Saturday threatened duties of 30% on products from Mexico and the European Union, two of America’s biggest trading partners, in an ongoing tariff campaign that’s upended global trade since he retook office in January.

President Donald Trump has announced that the European Union and Mexico will face a 30% tariff on imports to the US from 1 August.

Many of the policymakers were eager to end the economic uncertainty that Mr. Trump’s trade announcements had unleashed on German carmakers, Italian wine exporters and Irish pharmaceutical companies al...