Amid an increasingly bitter dispute with US aerospace giant, Boeing, the European Commission laid the groundwork on Wednesday for imposing retaliatory tariffs on €18 billion worth of American imports, a move that comes after the WTO said that the US had failed to remove some Boeing subsidies.

The US and EU have been battling for almost 15 years over subsidies given to Boeing and its European rival, Airbus. Brussels opted to take the extraordinary step to punish a close ally after President Do...