WASHINGTON (AP) — French President Emmanuel Macron drew sharp contrasts with President Donald Trump’s worldview Wednesday, laying out a firm vision of global leadership that rejects “the illusion of nationalism” in a candid counterweight to Trump’s appeals to put “America first.”

In the spotlight of a speech to the U.S. Congress, Macron was courteous but firm, deferential but resolute as he traced the lines of profound division between himself and Trump on key world issues: climate change, trade and the Iran nuclear deal.

A day after the French leader had put on a show of warmth and brotherly affection for Trump at the White House, his blunt speech prizing engagement over isolationism reinforced the French leader’s emerging role as a top defender of the liberal world order.

“We can choose isolationism, withdrawal and nationalism. This is an option. It can be tempting to us as a temporary remedy to our fears,” Macron said. “But closing the door to the world will not stop the evolution of the world. It will not douse but inflame the fears of our citizens.”

Issuing a bleak warning, he urged against letting “the rampaging work of extreme nationalism shake a world full of hopes for greater prosperity.”

It was a marked shift from the simpatico Macron of only a day earlier during his state visit at the White House. In his first year as France’s president, Macron has carefully cultivated as close a relationship to Trump as any world leader can boast. But addressing a joint meeting of Congress — an honor granted only occasionally to leaders of close U.S. allies — Macron confronted his differences with Trump head-on.

As Trump weighs pulling out of the 2015 Iran accord, Macron made clear that France will not follow his lead.

“We signed it at the initiative of the United States. We signed it, both the United States and France,” Macron said. “That is why we cannot say we should get rid of it like that.”

Macron later told French reporters that he has no “inside information” on Trump’s decision on the Iran deal but noted that it’s clear the U.S. president “is not very much eager to defend it.”