BRUSSELS — European Union diplomats in the United States have hired a prominent Republican-linked lobbying firm with ties to the first Donald Trump administration to advise on trade and investment communication strategy, according to documents seen by POLITICO.

U.S. President Donald Trump has hinted that the European Union could be the next target in his ongoing tariff battle. After imposing steep tariffs on China, Mexico, and Canada, Trump now claims the EU has been unfairly benefiting at the expense of the U.