Greece said it will launch military exercises Wednesday with France, Italy and Cyprus in the eastern Mediterranean, the focus of escalating tensions between Athens and Ankara.
The joint exercises south of Cyprus and the Greek island of Crete will last three days, the defence ministry said.
The discovery of major gas deposits in waters surrounding Crete and Cyprus has triggered a scramble for energy riches and revived old rivalries between NATO members Greece and Turkey.
Tensions ratched up another notch when Turkey sent the Oruc Reis research vessel accompanied by warships to disputed waters on August 10.
"Cyprus, Greece, France and Italy have agreed to deploy a joint presence in the eastern Mediterranean as part of the quadripartite cooperation initiative," the defence ministry said in a statement.
"The tensions and instability in the eastern Mediterranean have heightened disputes on issues concerning maritime space."
Turkey said on Tuesday it is ready for talks with Greece without preconditions over the row.
The olive branch came ahead of an informal EU foreign ministers' meeting in Berlin on Thursday and Friday at which Greece is expected to press the bloc to slap biting sanctions on its historic regional rival.
But EU nations would prefer to avoid irritating Turkish President Recep Tayyip Erdogan, and German Foreign Minister Heiko Maas shuttled between Athens and Ankara in a bid to temper the rhetoric and get talks back on track.
Maas, whose country holds the rotating EU presidency, told the two countries to defuse the row or risk sparking a "catastrophe".