Top EU officials have urged member states to live up to their responsibilities in solving the worst migration crisis since World War II or risk "tectonic changes" in Europe.
European Commission head Jean-Claude Juncker stressed there could be no passing the buck while European Council president Donald Tusk said the crisis threatened key achievements of the 28-nation bloc.
"I have no doubt that this challenge has the potential to change the European Union we have built. It has the potential even to destroy achievements such as border-free travel," Tusk told the European Parliament in the eastern French city of Strasbourg.
"And what is even more dangerous, it has the potential to create tectonic changes in the European political landscape. And these are not changes for the better," he said.
"These are truly extraordinary times that require extraordinary measures, extraordinary sacrifices, and extraordinary solidarity."
Tusk made his remarks as the UNHCR announced that more than 700,000 people fleeing war and upheaval in the Middle East and beyond had arrived in Europe so far this year.
More than 560,000 had landed first in Greece, with another 140,000 in Italy, straining their resources to the limit and causing chaos as they set off through the western Balkans trying to get to Germany and wealthier northern European Union states.
Hungary, Serbia, Croatia along with Germany and Austria have clamped down on their borders, trying to control and slow the influx but such actions have a knock-on effect as the migrants switch from one route to another in a desperate search for a way through.
Juncker, who on Sunday chaired an emergency migrants summit with Germany plus the EU and-non-EU Balkan states, said the bloc had to do better.
Having to organise repeated summits to try to get broad agreement on how to tackle the crisis only showed that the EU was "not in good shape", he added.