ISTANBUL (AP) — Amid an escalating war of words between Turkey and Greece over disputes in the Aegean Sea and the Mediterranean, both countries came together Tuesday to participate in an annual NATO naval exercise.

The neighbors and historic regional rivals are among 12 alliance members taking part in Dynamic Mariner-Mavi Balina 22 off Turkey’s western coast.

Relations between Turkey and Greece have worsened recently. Turkish President Recep Tayyip Erdogan issued a thinly veiled invasion threat a week ago when he said Turkey could “come all of a sudden one night” in response to perceived Greek threats.

The neighbors have decades-old disputes over an array of issues, including territorial claims in the Aegean and Mediterranean and disagreements over airspace limits. They’ve come to the brink of war three times in the last half-century.

Ankara claims that Greece is violating international agreements by militarizing islands close to its coastline, arguing that Greek sovereignty could be disputed if the alleged infringements continue.. It has also accused Greek air defenses of locking on to Turkish fighter jets during NATO exercises.

Greece has complained of Turkey’s rhetoric to NATO, the European Union and the United Nations. Athens says it needs to defend its eastern islands against its larger and militarily stronger neighbor.

It has also accused Turkey’s military of repeatedly violating Greek airspace and waters.

NATO announced the start of the joint exercise from Aksaz naval base near the Mediterranean resort of Marmaris. The war games run to Sept. 22.

“Dynamic Mariner is an incredibly important large-scale maritime exercise,” said French Vice Admiral Didier Piaton, deputy commander of NATO’s Allied Maritime Command.

“This year’s event includes more assets than ever before, facilitating increased interoperability between our nations and enhancing operational readiness. We continue to work closely with Turkey and other allies and partners to deter aggression and defend the alliance.”

The exercise incudes 50 ships, five submarines, five aircraft and 1,500 marines and other personnel.

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