A top European Union official, who is trying to head off a potential trade conflict, stressed the importance of active engagement and fairness in trade during a four-hour meeting with Trump administration officials on Wednesday.

Donald Trump’s tariffs are a headache for all his trade partners. But the U.S. president’s plan to impose ad hoc “reciprocal” levies on imports are a particular problem for the European Union. By enabling him to target whichever countries in the bloc he pleases,