Germany’s coalition government has split publicly over how to respond to Europe’s migrant crisis after its conservative interior minister proposed sending back refugees to countries bordering their war-torn homelands.

Thomas de Maiziere, whose handling of a massive influx of asylum seekers has prompted widespread domestic criticism, suggested that the EU should set an overall cap beyond which refugees would be sent back to the region of origin. But the idea was swiftly shot down by social democrat deputy chancellor Sigmar Gabriel as unconstitutional and contrary to government policy.

The split came as John Kerry, US secretary of state, announced in Berlin that the US would raise to 100,000, from 70,000 currently, the number of worldwide refugees it accepts annually by 2017. Most of the additional number would be from Syria.