The European Union is delaying until mid-April its retaliatory trade action over the Trump administration’s increase in tariffs on all steel and aluminum imports.

As one of the European Union's top negotiators, Sabine Weyand has battled Britain over Brexit and driven tough trade talks around the world. But as Europe seeks a deal to avert further U.S. tariffs, the EU's most senior civil servant for trade acknowledges one fundamental obstacle: Donald Trump's endgame remains a mystery.