EU officials told the Turkish government on Monday that it must "urgently" resume accepting migrants from Greece, where thousands are being held in camps, DW reports.
The bloc struck a deal with Ankara in 2016 that it would take back asylum seekers from Greek islands who had their applications rejected.
But tensions have flared between EU members Greece and Cyprus over a decades-old maritime dispute with Turkey.
"I call on Turkey to urgently resume the return of migrants from Greece," said EU Home Affairs Commissioner Ylva Johansson during a visit to the island of Lesbos, which hosts more than 8,000 asylum seekers.