European Commission President Jean-Claude Juncker has said that adding border checks to Europe’s passport-free area would cost at least three billion euros a year in lost business. Juncker, whose EU executive is working on revising the bloc’s asylum-seeking policy, told the European Parliament in Strasbourg on Wednesday that every hour of waiting time at borders had a cost.

“One after another, we close the borders and once they are all closed we will see that the economic cost is huge,” Juncker said, adding, “If we close the borders, if the internal market begins to suffer … then one day we will be wondering whether or not we really need a common currency if there is no single market, no free movement of workers any more.”

Juncker pointed out that he decided to stress the economic impact because of EU governments’ “cavalier” attitude to the Schengen zone of passport-free travel. The remarks come as some European governments have pledged to close their borders to incoming refugees from conflict zones.

On Tuesday, German Transport Minister Alexander Dobrindt told the Muenchner Merkur newspaper that Berlin must prevent refugees from crossing into Germany and even act alone if it cannot reach a Europe-wide deal on resettling them in the continent. German officials and politicians have intensified pressure on Chancellor Angela Merkel over her open-door refugee policy, which saw thousands of refugees arrive in Germany last year.

Merkel has pledged to “measurably reduce” arrivals in 2016, but has refused to introduce a cap, saying it would be impossible to enforce without closing German borders. Instead, she has tried to convince other European nations to take in quotas of refugees, has pushed for reception centers to be built on Europe’s external borders, and led an EU campaign to persuade Turkey to keep refugees from entering the bloc. But progress has been slow.

Europe is facing an unprecedented influx of refugees who are fleeing conflict-ridden zones in Africa and the Middle East, particularly Syria. Officials in European countries are struggling to forge a united response to the record numbers of refugees.

According to figures released by the International Organization for Migration (IOM), more than one million refugees reached Europe’s shores in 2015. More than 3,300 people either died or went missing in their perilous journey to the continent. Many blame major European powers for the exodus, saying their policies have led to a surge in terrorism and wars, forcing more people out of their homes.