“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.