European Commission President Jean-Claude Juncker warned that Europeans would find it harder to find jobs and the economy would suffer if Europe's internal passport-free travel zone collapsed. Many EU member states have threatened to pull out of the Schengen zone agreement as the refugee crisis in 2015 exposed bitter differences over migration policy.

The president also conceded that it would not be easy to curb the mass influx of migrants and refugees, but maintained that Schengen was one of the “biggest achievements of the European integration process."

"Less Schengen means less employment, less economic growth," he told a news conference in Brussels. "Without Schengen, without the free movement of workers, without freedom of European citizens to travel, the euro makes no sense,” he added.

Urging member states to fully adopt the measures the bloc has agreed upon, Juncker warned that a breakup of Schengen would also make freight and business travel much more expensive .

EU members have split into factions over the worst refugee crisis since World War Two, as Germany and Brussels point fingers at Italy and Greece for failing to regulate the flow of people across borders. In reply, the southern nations have severely criticized Berlin’s open-door policy, saying that it has encouraged more arrivals. Last year, more than a million refugees arrived in the EU.

Admitting that there was a tough battle ahead, Juncker said he would not give up seeking a solution to prevent member states from reintroducing border controls within Schengen.

“ I'm not going to give up, I reject the idea that this is somehow the beginning of an end," he said.