The Elgin Marbles, a set of Parthenon sculptures that Britain and Greece disagree about who owns, reached a breaking point on Tuesday when the leaders of the two countries cancelled a scheduled meeting.

The meeting between Prime Minister Rishi Sunak and Greek colleague Kyriakos Mitsotakis was canceled on Tuesday, according to his office. The two parties had earlier decided that the meeting should not be utilized as a public forum “to relitigate long, long settled matters”.

“It’s simply the case that if assurances are given and they’re not adhered to, that there are consequences for that,” Sunak’s spokesman told reporters.

A senior Greek government official speaking on condition of anonymity dismissed the statement as “inaccurate”.

Greece has repeatedly called on the British Museum to permanently return the 2,500-year-old sculptures that British diplomat Lord Elgin removed from the Parthenon temple in 1806, during a period when Greece was under Ottoman Turkish rule.

About half of the 160-metre frieze that adorned the temple is in London, while another 50 metres are in the Acropolis museum in Athens, whose top floor layout mimics the Parthenon.

Appearing on the BBC over the weekend, Mitsotakis compared the separation of the carvings to cutting the Mona Lisa in half, a characterisation rejected by the British government.