Greece has criticized the United Kingdom for canceling a planned meeting between Prime Minister Kyriakos Mitsotakis and UK Prime Minister Rishi Sunak, apparently so that Sunak could avoid talking about ancient artifacts that Greece says were taken illegally.

Mitsotakis and Sunak were set to meet on Tuesday, but Sunak canceled it on Monday, reportedly after learning that Mitsotakis planned to talk about the Parthenon sculptures.

The UK government initially believed Mitsotakis would not talk about the sculptures, which now reside in the British Museum. The sculptures were once part of the Parthenon in the Greek capital Athens.

The row escalated after Mitsotakis told the BBC on Sunday the UK's offer to store some of the sculptures in London and some in Athens was akin to cutting the Mona Lisa in two. He also said the sculptures had been "essentially stolen".

Mitsotakis said he was "deeply disappointed by the abrupt cancellation" of the meeting.

"Those who firmly believe in the correctness and justice of their positions are never hesitant to engage in constructive argument and debate," he was quoted by The Associated Press as saying.

The BBC reported that sources in the Greek government were "baffled" and "annoyed" by the meeting cancellation.

Greece has long criticized the way in which the Parthenon sculptures ended up in London, after they were bought by British diplomat Lord Elgin in dubious circumstances and shipped to the UK between 1801 and 1804. Because the two nations disagree on the legality of the transaction and have entrenched positions, they have tended to avoid talking about the issue during high-level diplomatic meetings.

The UK's Transport Secretary Mark Harper said on the BBC's Breakfast program on Tuesday that it was regretful the prime ministers would not meet during Mitsotakis' UK visit. He said Mitsotakis had been offered the chance to meet instead the UK's deputy prime minister, Oliver Dowden, but had declined.

"The views of Greece on the Parthenon sculptures are well known," Mitsotakis was quoted by The Guardian as saying. "I had hoped to have the opportunity to discuss them with my British counterpart along with other international challenges."

The UK's opposition Labour Party criticized Sunak for canceling the meeting and said his behavior appeared disrespectful.

"To pick a fight with a NATO ally for the sake of a headline shows just how weak Rishi Sunak is," a party spokesman told the BBC. "He should have been talking about the economy, immigration, the Middle East, that's what the country would expect from a leader, but Rishi Sunak is no leader."

Keir Starmer, the Labour Party's leader, described the apparent snub as "pathetic" and said he would like to see the sculptures returned to Greece through a loan arrangement.