Turkish President Recep Tayyip Erdogan called for dialogue on Monday while still pushing ahead with a contentious Mediterranean gas development plan that has outraged Greece and alarmed NATO and the EU.
The budding row over suspected reserves in the eastern Mediterranean Sea pits a range of regional powers in a confrontation watched with worry in Brussels and Washington.
Turkey dispatched a research ship to the region on Monday -- just three days after Erdogan said he was tired of waiting for the outcome of sporadic talks held in the past month with Greece and EU powerhouse Germany.
The vessel's arrival in an disputed area near the island of Meis (Kastellorizo in Greek) prompted Greek Prime Minister Kyriakos Mitsotakis on Monday to confer with his military chiefs.
Mitsotakis took no action but the Greek foreign ministry called the ship's arrival a "serious escalation" that "exposed" Turkey's "destabilising role".
Erdogan sounded a slightly more conciliatory note after a meeting with his own ministers later Monday.
"Let us all come together as Mediterranean countries and find a formula that protects all of our rights," Erdogan said in a national address.
But Erdogan added: "We cannot allow (nations) to ignore a big country like Turkey and try to imprison us to our shores."
- NATO and EU alarm -
The dispute is fanning longstanding regional tensions that flared up again with the military conflict in Libya.
Erdogan said last month he was "suspending" gas exploration to give time for talks with Greece and the EU's current president Germany.
But the mood soured when Greece and Egypt -- a rival to Turkey in Libya -- last week signed an agreement to set up an exclusive economic zone in the region.
The Turkish foreign ministry said the "so-called maritime deal" was "null and void".
Turkey's Oruc Reis vessel is planning to conduct seismic research at the easternmost edge of Greece's maritime jurisdiction.
The area is close to Turkey but belongs to Greece under international law.
Turkey says the rules are unfair since Greece only has rights to the waters because of a few tiny islands that expand its legal reach.
The European Union appears to be siding with Greece in the dispute.
The bloc's foreign policy chief Josep Borrell on Sunday called Turkey's actions "extremely worrying" and a recipe for "greater antagonism and distrust".
NATO Secretary General Jens Stoltenberg urged respect for international law during his talks on Monday with the Greek premier.
"The situation must be resolved in a spirit of Allied solidarity and in accordance with international law," Stoltenberg tweeted after speaking to Mitsotakis.