BERLIN (AP) – German Chancellor Angela Merkel stressed the need Thursday for a European approach to dealing with the influx of asylum seekers, as she sought to fend off critics from within her own conservative bloc while defending her 2015 decision to keep Germany’s borders open during the refugee crisis.

Speaking to Parliament before heading to a European Union summit in Brussels, she described the move to lawmakers as an exceptional gesture to help relieve pressure on nearby Austria and Hungary, whose leaders had personally appealed for assistance as migrants streamed into their countries.

“We said in an exceptional situation we will help and now, as then, I think it was the right decision,” Merkel said.

The German chancellor is fighting a battle at home and abroad against critics who accuse her of endangering European security with her welcoming approach to migrants. Merkel’s conservative bloc is under pressure from the far-right Alternative for Germany party that has received a surge in support since 2015, and populist leaders in southern and eastern Europe have rejected her calls a wholesale reform of Europe’s migration system.

Internal strife within her coalition has become so acrimonious that could bring down her government, but Merkel told parliament the implications were even broader.

“Europe has many challenges, but that of migration could determine the fate of the European Union,” she said.

Faced with the likelihood that the EU’s 28 members won’t be able to agree unanimously on an approach, Merkel said she would seek a “coalition of the willing” to agree on pressing measures to tackle illegal migration until a pan-European solution could be found.

“My maxim is: not unilateral, not uncoordinated and not at the expense of third parties,” she said.

Merkel said the EU’s members disagree on two key points – a common asylum policy and a fair distribution of refugees -and she doesn’t expect a deal this week. Still, she insisted that measures taken since 2015, both at the national and European level, were heading in the right direction.

Citing the killing of a girl by a young Iraqi asylum-seeker, and the inability of German authorities to deport a suspected former aide to Osama bin Laden , Merkel said there “is a need to act.”

In a nod to one of her fiercest critics at home, Interior Minister Horst Seehofer, Merkel also said she agreed on the need to prevent asylum-seekers from moving across the continent’s open borders at will. Refugees who enter the EU have to stay in the first country they registered in, but the so-called Dublin regulations haven’t been properly enforced, resulting in people making multiple asylum requests in different countries.

“A person who seeks protection in Europe can’t choose the country within the European Union where he or she wants to submit an asylum request,” she said. But she added that “we can’t leave those countries where all arrivals take place to fend for themselves.”

Seehofer, whose Bavaria-only party faces state elections this fall, has taken a tough line on migration, threatening to turn asylum-seekers who have registered in another country back at the border, putting him at odds with Merkel who rejects the unilateral approach and questions its legality.

Illustrating the complexities of the issue, Austrian Interior Minister Herbert Kickl said in an interview with Austria’s Puls 4 television that if Seehofer thought he could simply send migrants back to Austria, he should think again.

“If Germany believes that one can simply send people back to Austria in violation of international law, then we will explain to the Germans that we will not take these people,” Kickl said.

He said that Germany if believes another country like Slovenia or Croatia should be responsible for the asylum application in accordance with the Dublin rules, expelling them into Austria is not an option.

Kickl said he would tell Seehofer: “If they are already in Germany, then they stay in Germany. For us there is no reason to take these people back.”

He added that if the EU summit provided no solution, Austria takes over the rotating EU presidency on the weekend and could use the opportunity to try and develop a new model for a European asylum system.

“We need to address the problem to where it, in reality, arises,” he said. “And that is the exterior border of the European Union.”

The leader of Alternative for Germany, Alexander Gauland, called on Merkel to close the country’s borders and pursue “national interests.”