Prime Minister Kyriakos Mitsotakis of Greece stood before the United Nations Security Council on Thursday holding a map.
It showed a line drawn across the Mediterranean between Turkey and Libya that runs straight past Crete, Greece’s largest island, as if it were not there.
“Turkey and Libya have tried to draw a maritime border between them as if the Greek islands that lie between their coasts did not exist,” Mr. Mitsotakis said.
“These are not uninhabited rocks in the middle of the sea. These are thriving communities with centuries of history, where hundreds of thousands of people live. Geography cannot be rewritten.”
It was a rare piece of political theater at the council, and a measure of how seriously Athens takes the threat.
Mr. Mitsotakis called the deal “absurd” and said there was no precedent for such a diagonal boundary between two countries that share no facing or neighboring coastlines.
The 2019 agreement between Turkey and Libya’s government in Tripoli lay dormant for years as a largely symbolic claim, because Libya’s rival parliament in the east refused to endorse it. Last week, that parliament reversed course and ratified it.
The move handed Ankara a diplomatic victory and a fresh legal pretext to challenge Greek activity in waters Athens considers its own.
The stakes are concrete.
The contested waters lie along the route of a planned undersea power cable meant to link the grids of Greece and Cyprus, a project backed by the European Union to end Cyprus’ energy isolation.
A French survey ship arrived in Crete this week to resume work on the cable. In 2024, Turkish warships shadowed a similar vessel and forced the survey to stop.
Mr. Mitsotakis warned that the ratification must not become “a pretext” to obstruct lawful projects at sea.
He is effectively asking the world to watch what happens when the ship sets out, expected in early November.
Greece has worked hard to frame the dispute as a test of international law rather than a bilateral quarrel between two NATO allies.
This week it rallied the European Union, Cyprus, Egypt, Bahrain and the United Arab Emirates behind a joint statement at the United Nations calling the deal void, and the United States has called the ratification “provocative.”
Turkey has dismissed the objections as legally baseless.
Mr. Mitsotakis also pressed Europe to take a firmer role in protecting its shipping lanes.
“Europe cannot aspire to be a global economic power,” he said, “while remaining a spectator when the security of its trade routes is at stake.”
