Greece on Wednesday backed Cyprus in a row with Turkey over oil exploration, a day after the Cypriots accused Ankara of having resorted to 19th century-style gunboat diplomacy.
"I cannot say that Turkey's stance until now, and its general practices in the eastern Mediterranean leave much room for optimism," said Greek President Karolos Papoulias.
It was "unacceptable" that Turkey should "call into question sovereign rights concerning the exploitation of marine wealth that Cyprus has under international law," he said.
Papoulias was speaking after a meeting with his Cypriot counterpart Demetris Christofias, who on Wednesday began a three-day official visit to Greece.
Nicosia said the incident occurred off Cyprus' south coast on Nov. 13, when a Turkish warship turned back a Norwegian-flagged exploration vessel.
Cypriot Foreign Minister Marcos Kyprianou on Tuesday accused Turkey of resorting to 19th-century tactics.
"No modern state, especially one that wants to join the E.U., sends out warships to impede the (legal) exercise of rights," he said.
Ankara countered that the Greek Cypriot oil search mission had violated its territorial rights and vowed to protest to international bodies.
"Greece and Cyprus will remain vigilant to scrutinize Turkey's strategy and tactics," Christofias told reporters after his meeting with Papoulias.
"We are builders, not wreckers - but at the same time we will... defend the sovereign rights of Cyprus and Greece against schemes coming from this provocative neighbor," he said.
The internationally recognized Greek Cypriot government has signed gas and oil exploration deals with Egypt and Lebanon, sparking Turkish protests that the deals damage the rights of the island's breakaway Turkish Cypriot statelet.
Cyprus has been divided along ethnic lines since 1974 when Turkey occupied the northern third of the island in response to an Athens-engineered Greek Cypriot coup seeking to unite the country with Greece.
Greece also clashed with Turkey last week in a separate row over oil exploration.
On Nov. 15, a Norwegian survey ship commissioned by the Turkish government called off a search in the southeastern Aegean after Athens complained that the exploration was being conducted in its waters.