Athens and Ankara are at loggerheads as they compete for gas in the eastern Mediterranean.
Concerns are growing there could be a conflict between Turkey and Greece in the eastern Mediterranean.
For weeks, the two neighbouring countries have been disputing maritime boundaries and offshore energy rights.
On Tuesday, they sent warships to the waters in a show of force.
Turkey's vessel Oruc Reis is conducting research - and Greece says it is above its continental shelf.
Ankara disputes Athens' exclusive rights in the region.
Both countries have announced military exercises within a broad area between the Greek island of Crete and Cyprus.
But they have also signalled readiness for dialogue as Germany tries to mediate between the NATO allies.
So, could this dispute escalate? And what would it take to defuse it?