European Union (EU) countries are poised to restrict passport-free travel by invoking an emergency rule to control borders as the refugee crisis continues, according to EU documents seen by The Associated Press.
The rule would be in place for at least two years, the news agency said on Friday, and would reverse a decades-old trend of expanding passport-free travel in Europe.
The news came as EU member states gave Greece a three-month ultimatum to remedy "deficiencies" in controlling the refugee flow or face border controls with the rest of the Schengen passport-free zone, EU sources said, also on Friday.
The EU told Greece "that given the scale of the situation, further efforts are needed".
Since 1995, people have been able to cross borders among Schengen Area member countries without document checks.
Each of the current 26 countries in the Schengen Area is allowed to unilaterally put up border controls for a maximum of six months, but that time limit can be extended for up to two years if a member is found to be failing to protect its borders.
The documents show that EU policy makers are preparing to make unprecedented use of that provision by declaring that Greece is failing to sufficiently protect its border.
Some 2,000 people a day are still arriving daily on Greek islands from Turkey, most of them keen to move to countries including Germany and Sweden.
In the 43 days of 2016 so far, at least 410 refugees have died on the way to Europe.
Greek government officials declined to comment on the documents.
READ MORE: Female refugees face sexual exploitation in Greece
In November, European inspectors visited Greek border sites and gave Athens until early May to upgrade the border management on its islands.
Two draft assessments forwarded to the Greek government in early January indicated Athens was making progress, although they noted "important shortcomings" in handling refugee flows.
With asylum-seekers still coming at a pace 10 times that of January 2015, European countries are reluctant to dismantle their emergency border controls.
If they keep them in place without authorisation, EU officials fear the open-travel zone concept could be brought down.
READ MORE: Hundreds of refugees died on way to Europe this year
Greece says it has already addressed many of the European concerns. It has promised to complete new screening centers on four Greek islands and build two new transit camps within the next week, with the help of the country's armed forces.
With a sense of compromise, Friday's EU statement acknowledged the vast challenge facing Greece, saying "the very large number of arrivals is such that the external border controls of any member state would be placed under severe pressure".
But it stressed that the concept of Schengen needed to be preserved.
"The difficulties faced by Greece have an impact on the EU as a whole, and have to be resolved collectively," it said.
So far, six Schengen members have imposed border checks, and many of those would have to dismantle them starting in mid-May under Schengen rules.
Germany has until May 13, and has made clear that it does not want to relinquish the checks. The other countries are France, Austria, Denmark and Norway.