Greece has used its turn at the helm of the United Nations Security Council to rally an unusual coalition against Turkey.
The European Union, Cyprus, Egypt and two Persian Gulf monarchies joined Athens in declaring a contested Turkey-Libya maritime pact "null and void."
Foreign Minister Giorgos Gerapetritis of Greece read the joint statement on behalf of Greece, Cyprus, the European Union, Egypt, Bahrain and the United Arab Emirates.
He warned that Libya's ratification of the deal last week threatened stability across the Mediterranean.
"Accepting bilateral agreements that disregard the applicable rules and principles of international law would set a dangerous precedent," Mr. Gerapetritis told the council, which Greece is presiding over this month.
The signatories are as significant as the words. Bahrain and the Emirates have no direct stake in the waters off Crete, and both maintain working ties with Ankara.
Their willingness to stand publicly with Greece reflects Athens' deepening partnerships in the Gulf. Just last week, Greece agreed to keep its Patriot missile battery in Saudi Arabia, and Abu Dhabi's crown prince visited Athens with deals worth up to 12 billion euros.
The 2019 memorandum, signed between Turkey and Libya's government in Tripoli, draws a maritime boundary that ignores Greek islands, including Crete.
For years it was dismissed as a paper claim, because Libya's rival parliament in the east refused to endorse it.
That changed last week, when the eastern lawmakers ratified it, handing Ankara a diplomatic victory and stronger grounds to challenge Greek projects at sea.
Pressure on Turkey has been mounting. On Sunday, the U.S. State Department called the ratification "provocative," a notable hardening of Washington's usually cautious tone.
On Monday, U.N. Secretary-General António Guterres said the force of law must prevail over the law of force. Turkish President Recep Tayyip Erdogan, for his part, dismissed European objections as legally baseless.
The confrontation may soon move from diplomacy to the sea. A French survey ship is due in Crete on Tuesday to resume work on an undersea power cable linking Greece and Cyprus, a project Turkey opposes on the strength of the Libya deal.
Two years ago, Turkish warships forced a halt to similar work.