Greek Prime Minister Kyriakos Mitsotakis met with British Museum chair George Osborne in London last week to discuss the potential repatriation of 5th-century BC Parthenon sculptures to Athens, Greek newspaper Ta Nea reported.

Secret talks have been underway for more than a year, according to the report. Osborne, the former U.K. chancellor of the Exchequer, has also met with two senior Greek government ministers, the paper said.

The Parthenon sculptures are better known as the “Elgin Marbles” — after the English earl and diplomat to the Ottoman Empire who removed the treasures from the Ancient Greek Parthenon temple in the early 1800s, then sold them to the British Museum. The works have been a flash point between the two countries and a long-running art world debate ever since.

“An agreement is 90 percent complete, but a critical 10 percent remains unresolved,” a person close to the talks told the newspaper. “It’s hard to get there, but it’s not impossible. Significant progress has been made.”

Last week, Mitsotakis sounded a positive note over the issue. “A win-win solution can be found that will result in the reunification of the Parthenon sculptures in Greece, while at the same time taking into account concerns that the British Museum may have,” Mitsotakis said.

A possible solution, dubbed the “Palermo model” for having been used with works in dispute with a museum in Sicily, would see the Parthenon sculptures “deposited” in the Acropolis Museum in Athens for a temporary period, after which the governments would announce a deal for the treasures to stay permanently, according to Ta Nea. Such a deal could be agreed on without explicitly mentioning ownership of the artefacts.

“I don’t think anyone is seriously thinking that when the marbles go back [to Athens] they won’t go back permanently,” former U.K. Culture Secretary Ben Bradshaw told Ta Nea.