Prime Minister Kyriakos Mitsotakis insists that Greece will not accept any arrangement over the Parthenon Marbles that recognizes foreign sovereignty over them, or any loan of what he called Greece's own treasures, in his sharpest public message to London in weeks.
Speaking at the Museum of Byzantine Culture over the weekend, Mr. Mitsotakis said the time had come for "truth, logic, justice and morality."
He said the Marbles must be displayed together, in direct visual contact with the Acropolis rock for which they were carved, a purpose the Acropolis Museum was built to serve. The monument, he said, "unfortunately remains violently dismembered."
The remarks follow reports that talks between Athens and the British Museum have stalled over ownership.
The museum, which is barred by British law from permanently removing items from its collection, says discussions remain constructive and has suggested a long-term loan arrangement. Greece rejects a loan because it implies the museum's ownership.
Mr. Mitsotakis tied the Marbles to the day's ceremony, in which Greece and Bulgaria signed protocols returning 48 religious relics taken from Serres to Sofia in 1917 and sending to Bulgaria the remains identified as Tsar Samuel's.
"Monuments cannot be treated as spoils of war," he said, adding that the principle of a monument's integrity runs through Greece's campaign for the Marbles.
Bulgarian Prime Minister Rumen Radev, who also spoke, thanked Mr. Mitsotakis for helping secure what he called a historic agreement.
Mr. Mitsotakis said talks on the relics began about 50 years ago between Konstantinos Karamanlis and Todor Zhivkov and finished only now because old rigidities were overcome. He said he expects more returns to follow.