Donald Trump’s decision to slap tariffs on countries that have shown support for Greenland is pushing transatlantic relations to a breaking point as EU leaders contemplate ways of retaliating against Washington that until now have been unthinkable.

One option being floated by centrist and left-wing politicians is for Europe to wheel out its Anti-Coercion Instrument, the EU’s so-called trade “bazooka” — a powerful retaliation tool that was originally conceived to fend off bullying from China, which would allow Europe to impose tariffs and investment limits against offending nations.

French President Emmanuel Macron has joined those calling for the instrument to be deployed against the U.S.