Greece's culture minister has said he will not launch a court challenge for the Elgin Marbles to be returned to Athens.
The sculptures, which for more than 2,000 years decorated the Parthenon temple on the Acropolis in Athens, were removed more than two centuries ago by Lord Elgin, a Scottish nobleman, and are on display at the British Museum in London.
Culture minister Nikos Xydakis said Athens would not seek court action against the museum but preferred a "diplomatic route".
Dennis Menos, of the International Association for the Reunification of the Parthenon Sculptures, said the decision by the new government in Athens had "devastated the Greek position".
"I'm sorry that this statement was made. (Court action) was always an option and now that has been eliminated," Mr Menos said.
The prospect of a legal challenge gained momentum last year when a team of London lawyers, including Amal Clooney, wife of US film star George Clooney, visited Athens and met officials from Greece's previous conservative government.
Mr Xydakis, the culture minister, said the legal initiative was funded by an anonymous private donor and was still ongoing.
But he added, speaking to private Mega television: "It's a diplomatic route and a political one for (Greece). You cannot go to court for every issue. And in international court, the outcome is always uncertain. Things are not that simple."
The Acropolis Museum, which opened at the foot of the ancient citadel in 2009, was built in part to house the Parthenon marbles if they are returned. The site is the most visited museum in Greece, attracting nearly 1.4 million visitors in 2014.