Europe's cherished free-travel zone will shut down unless Turkey acts to cut the number of migrants heading north through Greece by March 7, European Union officials say.
Their declaration came as confrontations grow increasingly rancorous among European countries trying to cope with the influx of refugees. Those recriminations culminated in Greece recalling its ambassador to Austria on Thursday.
"In the next ten days, we need tangible and clear results on the ground," the top EU migration official, Dimitris Avramopoulos, said after EU justice and home affairs ministers met in Brussels on Thursday.
"Otherwise there is a danger, there is a risk that the whole system will completely break down."
EU leaders are now pinning their hopes on talks with Turkey on March 7 and their own migration summit on March 18-19 before warmer weather encourages more arrivals across the Mediterranean.
Seven European states have already restored border controls within the creaking Schengen passport-free zone.
More said they would unilaterally tighten border controls unless a deal with Turkey shows results before the two March summits.
That deal promises Turkey 3 billion euros ($A4.59 billion) in aid to help it shelter refugees from the Syrian war, in return for preventing their travelling on to Europe.
"By March 7, we want a significant reduction in the number of refugees at the border between Turkey and Greece," German Interior Minister Thomas de Maiziere said.
"Otherwise ,there will have to be other joint, coordinated European measures."
Germany has been pushing the Turkey plan hard. Many other EU states are increasingly frustrated and sceptical, though.
Another 110,000 people have arrived on the continent so far this year, mostly from Turkey via Greece, after more than a million arrived last year.
NATO has agreed to send ships to the Aegean to help fight people-trafficking, and one military official said the aim was to have the mission running before March 7.
The crisis was exacerbated when German Chancellor Angela Merkel last year waived EU procedures to take in hundreds of thousands of Syrians. Mutual recriminations have sabotaged efforts to share the burden systematically ever since.
"We have no policy any more. We are heading into anarchy," said Jean Asselborn, Luxembourg's foreign minister.
Belgium, France, Germany, Norway, Sweden and Denmark have all introduced emergency border checks, allowed under the Schengen rules.
But Austria, the last stop for most migrants before Germany, infuriated Brussels and Berlin last week by setting daily caps on the number of people it processes.
The decision set off a cascade of similar moves back through the western Balkans, the main migration route, leaving ever more migrants stuck in Greece.
"If Greece is not able or willing to secure the EU's external border, others have to act," Austrian Interior Minister Johanna Mikl-Leitner said.
"If Greece insists that it cannot protect the Greek border, one has to ask themselves whether the Schengen border should be there."
