European Council President Donald Tusk has warned illegal economic migrants against coming to Europe, during a new push to solve the EU migrant crisis.
He said illegal economic migrants were risking "lives and money" for nothing.
Mr Tusk visited Greece and Turkey on Thursday to discuss ways to reduce the flow of migrants travelling west.
More than 25,000 migrants have been left stranded in Greece by a tightening of border controls to the north, raising fears of a humanitarian crisis.
On Thursday, a group of migrants blocked a railway line on the Greek side of the border with Macedonia to protest at the restrictions.
They were imposed after several Balkan countries decided only to allow Syrian and Iraqi migrants across their frontiers. Austria also decided to limit numbers.
The move effectively barred passage to thousands of people seeking to reach Western Europe, including Afghans as well as some more likely to be regarded as economic migrants.