The European Union's fate rests on its ability to rise to the challenges of the migration debate, Chancellor Angela Merkel told the German parliament on Thursday ahead of a crunch summit in Brussels that will be dominated by the matter.

In a passionate address to the Bundestag, an embattled Merkel tried to win over critics from within her own ranks, defending her 2015 decision to open Germany's doors to a million migrants as a necessary step of help to its neighbours.

Calling for refugee harbouring agreements with African countries mirroring those that the EU sealed with Turkey, Merkel told a rowdy legislature that with falling migrant numbers, the tighter immigration controls of before 2015 must be re-established.

"Europe faces many challenges, but that of migration could become the make-or-break one for the EU," she concluded.

"Either we manage it, so others in Africa believe that we are guided by values and believe in multilateralism, not unilateralism, or nobody will believe any longer in the system of values that has made us strong," she said. "That's why it's so important."