German Chancellor Angela Merkel vowed to keep lobbying President Donald Trump to head off tariffs on U.S. auto imports, which could escalate a trade war and threaten the global economy.

“On the issue of trade, we have a very serious situation in the world, I want to make that very clear,” Merkel told reporters Friday in Berlin. Potential auto tariffs are “really a danger for the prosperity for many in the world” and would be viewed by Germany as a violation of global trade rules, likely provoking retaliation.

Tensions over trade are intensifying ahead of a meeting next week in Washington between Trump and European Commission President Jean-Claude Juncker. The bloc is set to propose exploring the possibility of reducing car tariffs for several key trade partners, people with knowledge of the plans said earlier this week.

Juncker will make “proposals about how we could get into a discussion process” to avert the threat, Merkel told reporters at her annual summer press conference. “We believe that we would be causing harm on both sides. That’s the position Jean-Claude Juncker will take with him.”

Trump Target

Germany’s export success has been a frequent target of Trump’s attacks. The U.S. president recently referred to Europe as a “foe” on trade issues, days after a contentious meeting with NATO allies including Germany. Levying tariffs on imported vehicles including Mercedes-Benz, BMW and Porsche models would represent a significant blow to Germany’s trademark industry.

Merkel reiterated her assertion that Europe can no longer count on the U.S. for stability even if trans-Atlantic relations remain critical.

“What we assumed for many decades, that the U.S. is a power that preserves peace – that is no longer a certain factor for the future,” she said.

Asked whether she views Trump as trustworthy partner, Merkel said she won’t give up on trans-Atlantic cooperation. “It’s not as self-evident as we were used to in years past. That means we also have to carry out conflicts more often,” she said.

Political Squabbling

Domestically, Merkel has weathered a political storm over migration policy with Bavarian allies that threatened her 13-year hold on power. Support for her CDU/CSU alliance has slumped to 29 percent in a July 16 poll from INSA, below the 32.9 percent result in September elections. Given the political crisis, “we can’t really be that mystified by the result,” the chancellor said.

Before embarking on a break for a few weeks without any public appointments, Merkel called for a multilateral approach, rebuking Trump’s unilateralism.

“You can see that the values and the order that we’ve all become accustomed to are strongly under pressure,” said Merkel. “It is the case that the issues that are important to me and my work, my solid commitment to multilateralism, to working together, to moving toward a win-win situation in that we have advantages for all – that these are not exactly the dominant principles operating today. But I’ll continue to push for it.”