German Chancellor Angela Merkel insisted on Tuesday that an EU-Turkish deal was the best way to help resolve Europe's refugee crisis and to head off the threat posed to passport-free travel in the bloc by sealing off national borders.
Merkel was speaking ahead of a key European Union leaders summit this week in Brussels, which is due to discuss steps to deal with the influx of refugees into the EU, including control of the flow via Greece to northern Europe.
"I will put all my strength on Thursday and Friday behind the European-Turkish approach as the best way to proceed," Merkel told a press conference in Berlin.
She also rejected a proposal by the group of Visegrad states – the Czech Republic, Poland, Hungary and Slovakia – calling for sealing off the so-called "Balkan" route to Europe by closing the border between Greece, Macedonia and Bulgaria.
In her comments, the chancellor warned of "all the consequences for Greece and the EU as a whole and therefore the Schengen area" from such a proposal. She was referring to the Schengen Treaty which established passport and visa free travel in the bloc.
Merkel said the only way to tackle the causes behind people wanting to flee their homelands and to shore up the EU's external borders was through cooperation with Ankara.
In Brussels, the European Commission President Jean-Claude Juncker joined the criticism of calls for border fences, warning that it could lead to the renewed fragmentation of Europe.
"Either we are a continent or we are a grouping that subdivides itself into national categories. It is the wrong path that some member states are in the process of taking," he told national parliamentarians.
In Athens, European Council President Donald Tusk warned that removing Greece from the Schengen zone because it is the gateway for migrants striving to reach Europe's wealthy core will not solve any problems.
Merkel needs to win EU backing for her refugee plans to help head off a damaging row in her conservative political bloc over asylum policy and to fulfil her pledge of "a drastic reduction" in new arrivals this year.
In addition to Merkel's proposals for strengthening the EU's external borders and combating illegal migration, she wants member states to share the burden of the refugees arriving in Europe.
However, the chancellor's call for further quotas for distributing refugees has met with stiff opposition from other EU members, in particular the Visegrad states.
Leading members of Merkel's ruling coalition also moved on Tuesday to lower expectations about the EU leaders reaching an agreement on how to handle the refugee crisis.
German Foreign Minister Frank-Walter Steinmeier told the TV news channel n-tv that he saw no reason to be "overoptimistic" about the outcome of the summit, adding that he was not expecting the leaders to reach any final decisions.
"Excluding Greece from Schengen solves none of our problems. It does not end the war in Syria. It does not end Europe's attraction of migrants," Tusk told reporters after meeting Greek Prime Minister Alexis Tsipras.
Athens said Greece has now established four of five hotspots - major centres for reception and registration of migrants that are a key ingredient of the EU plan for processing asylum seekers.
The leaders are expected to call for an "end to the 'wave-through approach'" that has allowed migrants and asylum seekers to travel largely unhindered from Greece through the Western Balkans and on to wealthy countries such as Germany, according to a draft statement seen by dpa.
They are also expected to demand "further, decisive efforts" from Turkey, which has been the departure point for those travelling to Greece. The other theme of the summit is agreeing on the British reforms deal.
Regardless of all plans to control the surge - which has seen around 1 million migrants reach Western Europe after crossing Greece, Macedonia, Serbia, Hungary or Croatia and Slovenia - Austria on Tuesday said it is putting additional measures in place for a quick sealing of its borders.
"We will therefore strengthen border control efforts in a massive way," Chancellor Werner Faymann told reporters in Vienna.