When European Commission President Jean-Claude Juncker left for Washington to meet with President Donald Trump, his mission was to try to dissuade the American president from escalating trade tensions between the U.S. and EU.
Then Mr. Trump started tweeting. “Tariffs are the greatest!” Mr. Trump declared early Tuesday. “Either a country which has treated the United States unfairly on Trade negotiates a fair deal, or it gets hit with Tariffs,” the president tweeted. Mr. Trump’s message surfaced as Mr. Juncker was en route....