European powers should not allow the United States to impose limits on their support for Ukraine, according to French President Emmanuel Macron, who invoked his country’s nuclear weapons arsenal as a basis for staring down Russia.

“We’re in a situation where we’re not quite sure about the European limits — why should others, other continents, tell us where our limits are?” Macron said during a wide-ranging speech at Sorbonne University, according to a France24 interpreter. “It’s a question of the security of Europe — are we prepared for that? No. We have to become credible and we have to be present and act as a force of deterrence. And this involves nuclear forces.”