Turkey has said it will release two Greek soldiers it has imprisoned once eight of its own servicemen are returned home from Greece, where they fled after a failed coup attempt. Athens says this amounts to "blackmail".
Greece says it won't allow two of its soldiers, who are currently being detained in Turkey, to be used as "bargaining chips" in an ongoing row between the two countries.
Turkish President Recep Tayipp Erdogan said he would consider releasing the soldiers if eight Turkish servicemen, who sought assylum in Greece following the failed 2016 coup attempt, were sent home first.
Athens has described this as "blackmail", with the Defence Ministry describing the soldiers as "hostages", and the Greek Supreme Court has sided with the government.
President Prokopis Pavlopoulos of Greece said:
"There was an unacceptable connection made between the Greek officers who were arbitrarily detained, and Turkish citizens who came to Greece, and requested asylum. Because Greece implemented - I emphasize this - implemented international law, it was granted. These are two totally different cases and any confusion is unthinkable"
The Turkish authorities have kept the two Greek soldiers in pre-trial detention in a prison in Edirne since they wandered onto Turkish terroritory by accident in March. No official charges have been filed against them.
There have been numerous street protests in Greece calling for their immediate release.