ATHENS — A controversial maritime border deal between Libya and Turkey has riled Greece, annoyed the European Union — and could intrude on Friday’s EU leaders’ summit.

Greek Prime Minister Kyriakos Mitsotakis will raise the issue during the informal meeting of EU leaders in Dublin, according to a senior official in Athens who spoke on condition of being granted anonymity. The summit is supposed to focus on AI and Ukraine.

The row centers on a Turkey-Libya agreement that claims a corridor in the eastern Mediterranean between Greece and Cyprus — waters Athens says fall within its exclusive economic zone and where the EU has backed energy and connectivity projects.

“Greece has explicitly stated … that in the event of any escalation, it will request sanctions and support from the European Union,” Greece’s Foreign Minister Giorgos Gerapetritis said last week in an interview with local TV.

Despite being NATO allies, Greece and Turkey have quarreled over maritime boundaries and overlapping claims to their continental shelves. Athens fears Ankara could invoke the Libya deal to challenge offshore exploration south of Crete and the EU-funded undersea electricity cable linking Greece and Cyprus, turning both projects into flashpoints.

Turkey signed the agreement in 2019 with Libya’s U.N.-backed government in Tripoli, and it was unanimously ratified by rival authorities in eastern Libya on Oct. 20.

The EU immediately responded.

“This agreement infringes upon the sovereign rights of third states, it does not comply with the Law of the Sea, and is null and void,” said a joint statement on Oct. 20 from the heads of the European Commission and Council.

Egypt also rejected the border pact, as did Bahrain, Cyprus (which has its own separate disputes with Turkey over Ankara’s occupation of the northern part of the island since the 1970s), Israel and the United Arab Emirates.

Turkish foreign ministry accused Brussels of adopting what it called the “maximalist and illegal” positions of Greece and Cyprus that were “detached from reality.”

“We expect them to respect the joint will of our country and Libya,” Turkish President Recep Tayyip Erdoğan said during a recent Cabinet meeting.

Mitsotakis raised the issue at last month’s U.N. General Assembly, and Athens is now pressing the rest of the EU for stronger action.

“There is no precedent for such a diagonal delimitation,” he said in New York, holding up a map to illustrate Greece’s position. “Geography cannot be rewritten … and sovereign rights cannot be erased by drawing arbitrary lines on a map.”

The underwater border demarcation is part of a broader Turkish policy of stressing its sovereignty over coastal areas. Ankara aims to codify what it calls its Blue Homeland doctrine by year’s end.

The big test

Greece and Cyprus warn that Turkey’s claims could be used to block strategic projects in the eastern Mediterranean.

The EU’s latest report on Turkey’s stalled EU accession progress specifically referred to Ankara’s continued obstruction of a €1.9 billion electricity interconnection between Greece and Cyprus. The project was interrupted in 2024 amid a standoff between Athens and Ankara.

Three months ago, French company Meridiam became the project’s majority shareholder.

On Tuesday, a French vessel sailed from Heraklion, Greece, to start working on the project. Gerapetritis told a parliamentary committee last week that Athens is bracing for a Turkish reaction.

Tension over the maritime border and the energy project comes as Turkey’s already difficult ties with the EU — from protecting the car industry to Ankara’s role in Black Sea security — come under greater pressure, noted Carnegie Europe Turkey analyst Marc Pierini.

“In the eastern Mediterranean, several divergences over maritime borders have widened the gap between Turkey and EU governments,” wrote Pierini.