German Chancellor Angela Merkel championed Europe, dismissed Brexit and said efforts to fight climate change are irreversible in a combative speech ahead of the Group of 20 summit that’s shaping up to be a confrontation over the direction of global policy. Merkel, in a speech to lawmakers in Germany’s lower house of parliament on Thursday, noted that “the world has become less united” and acknowledged that discussions at the G-20 meeting in Hamburg on July 7-8 “will be very difficult.” “The discord is obvious and it would be dishonest to paper over the conflict,” she said. Merkel is preparing to host world leaders including U.S. President Donald Trump, Russia’s Vladimir Putin and Xi Jinping of China amid a global shake-up that threatens much of the international order on issues established since World War II. On the agenda for the meeting are free trade, climate change and migration. G-20 nations, from Australia to Brazil, make up about two-thirds of the world population. G-20 Challenges In a swipe at Trump’s “America First” rhetoric, the chancellor said that nations turning to isolation and protectionism are making a serious mistake and showcased a renewed “spirit of unity” in the European Union after the U.K. decision to exit. All the same, the G-20 takes place “amid a particular set of challenges,” she said. “I’m convinced that we need the G-20 more urgently than ever before, because we can only move things together,” Merkel said. “Whoever believes that you can solve problems through isolation and protectionism is making a grave error.” The German leader reserved her most dramatic language for the Paris climate treaty after Trump pulled out of the global accord aimed at confronting climate change, which Merkel called “irreversible and not negotiable.” “We want to tackle this existential challenge and we can’t and we won’t wait until the last person on earth is convinced of the scientific basis for climate change,” Merkel said. In response to Trump’s inward shift, Merkel played up new French President Emmanuel Macron as an ally, saying the German-France axis will drive forward European unity, “regardless of Brexit.” She is hosting Macron in Berlin on Thursday along with European leaders including the U.K.’s Theresa May and Paolo Gentiloni of Italy to align their position ahead of the G-20. “It’s clear to both of us that German and French interests are extremely closely linked when it comes to Europe’s future,” she said. Balancing China While Merkel has reached out to China as a partner on climate change and free trade, she’s also warning Chinese investors that they may face restrictions in Europe. Germany’s government is “thinking about defining industrial sectors of strategic importance for Europe,” Merkel said in an interview with business weekly WirtschaftsWoche published Thursday. “For instance, we decided to resume major investments in microchips. If countries like China want to buy up what was just built up with a lot of subsidies, we have to react.” G-20 members meeting in Hamburg next week must send “a signal of determination that they have understood their overarching responsibility for the world, and that they are willing to act upon it,” she said.