German Chancellor Angela Merkel has called for the European Union to be exempted from new US tariffs on steel and aluminium imports.
"The best option would be [for the EU] to be excluded," she told business leaders gathered in Munich.
Ms Merkel warned that no one could win a "race to the bottom" and said the tariffs risked "hurting everyone".
President Donald Trump says the US has suffered from "unfair trade" and that the tariffs will boost industry.
The import duties - 25% on steel and 10% on aluminium - will go into effect in 15 days, although Canada and Mexico will be exempt while negotiations continue over the North America Free Trade Agreement (Nafta).
Mr Trump signed the declaration in a White House ceremony attended by American workers from both industries.