European leaders have said they would prefer to negotiate. If that fails, their response could go beyond anything they’ve tried before.

The auto tariffs will be felt sharply in Europe, for whom the U.S. is the biggest export market for an industry that supports nearly 14 million jobs.

European automakers, already struggling with tepid economic growth at home and looming Chinese competition, on Thursday decried the U.S. import tax on cars as a new, heavy burden that would hurt compa