Germany's Chancellor Angela Merkel and Greece's Prime Minister Alexis Tsipras chat after a family photo at a meeting over the Balkan refugee crisis with leaders from central and eastern Europe at the EU Commission headquarters in Brussels, Belgium, October 25, 2015. [Photo/Agencies]

Frustrated by the way nearly half a million people have been able to cross Greece largely undocumented this year, other EU states are using a mixture of financial incentive and promises to take in asylum-seekers from Greece - if Athens cooperates and, after weeks of delay, starts registering all who arrive.

Among other elements of the plan, EU member Slovenia will receive 400 extra police to handle an influx of migrants this month following Hungary's closure of its border with Croatia.

Merkel stressed, however, that lasting solutions to the crisis would take a long time yet.