European leaders warned on Monday that U.S. President Donald Trump's threat to expand tariffs to the EU risked igniting a trade war that would harm consumers on both sides of the Atlantic.

BRUSSELS—European leaders, bracing for a fight with President Trump over the world’s most valuable trading relationship, said they are ready to strike back but prefer cooperation. Trump over the weekend announced punishing tariffs on Canada and Mexico and made clear that U.

The threat of a transatlantic trade war loomed large Monday over a gathering of European leaders aimed at boosting the continent's defences in the face of an aggressive Russia.