Greece is calling on the EU and others to help secure the release of two of its soldiers arrested in Turkey last week.
Athens says the pair had been on a border patrol, when they strayed because of bad weather.
"Turkey is a member of NATO, an ally of Greece in NATO and this kind of incident needs to be solved via peaceful ways, and after negotiations between the two armed forces," said Greek Defence Minister Panos Kammenos, in Brussels.
The soldiers were reportedly picked up in a heavily-forested frontier region.
Turkish officials were not immediately available for comment at the time, but Turkey's state-owned Anadolu news agency has said the soldiers were detained on grounds of attempted military espionage and entering a prohibited military zone.
The soldiers have been remanded in custody by a Turkish court.
'Swift and positive outcome'
Brussels wants to see a swift outcome.
EU foreign policy chief Federica Mogherini told reporters: "It is extremely important to have good neighbourly relations, this is something we always convey to our Turkish interlocutors to all different levels, including mine. It has been extremely important for us to share this information and also to express our full hope that there will be a swift and positive outcome."
Reporting from Brussels, Euronews' Efi Koutsokosta said: "An EU-Turkey Summit, scheduled for the 26th of March in Varna, Bulgaria, is up in the air. The President of the EU Council said that it will take place under the condition that Turkey stops its provocations over the exclusive economic zone of Cyprus and the Aegean.
"According to EU diplomatic sources, the channels of communication with Turkey are open but the talks 'are not always pleasant.'"