"There is a major engagement on the part of Greece and Turkey towards sending 500 people back on April 4, barring a last-minute problem," the source told AFP on Thursday.
Those returning will be "Syrians who have not requested asylum, Afghans and Pakistanis", the official added, confirming that this is the first return set to take place under the EU-Turkey deal.
The official did not specify from which of the five Aegean Sea islands currently hosting refugees and migrants the operation will take place, nor whether it will take place via sea or air.
There are over 51,000 refugees and migrants trapped in Greece and hundreds continue to arrive on a daily basis from Turkey, despite the EU deal on limiting the influx nominally taking effect on March 20.
This includes over 11,000 people at Idomeni on the Greek border with Macedonia and some 5,700 at the port of Piraeus near Athens, waiting in vain for Balkan states to open their borders and permit them passage to northern Europe.
