Italy is pinning the blame on the John Paul Getty Museum in Los Angeles for a halt in the return of pillaged art treasures.

"The talks broke down because they suspended them. It was a unilateral decision," Culture Minister Francesco Rutelli said Thursday.

The Getty has halted the return of stolen artefacts in a fresh dispute over a magnificent bronze statue of an athlete.

The Getty's curator, Michael Brand, wrote to Rutelli two days ago to express his "deep regret" that 20 out of an earmarked batch of 46 works would be retained.

Rutelli, who will be in New York next week for related talks with the Metropolitan Museum (Met) on Italy's new drive to regain lost treasures, voiced "surprise and disappointment" at the Getty's move.

The artefacts which the Getty has decided to keep include a bronze statue of an athlete attributed to the Greek sculptor Lysippos, which the Californian museum acquired in 1977.

It was found off in the Adriatic, off the Marche port of Fano, in 1964. In an apparent about-turn on the question of the masterpiece's provenance, the Getty has now reverted to a previous claim that it was found in international waters and does not belong to Italy.

Italy does not dispute that the bronze was outside territorial waters when it was discovered, but stresses that it was taken out of Italy illegally.

The Lysippos bronze has proved the main sticking point in implementing a preliminary agreement reached last month.

"We regret the fact that this object stands in the way of an accord but our conscience is clear in keeping the work," Brand said in the letter to Rutelli.

In the case of another now-withheld masterpiece, a marble Venus found at the Ancient Greek colony of Morgantina new Enna, Sicily, Brand said the Getty would have been willing to return it - in joint ownership - if joint investigations established it had been plundered.

But that prospect has faded with the breakdown in negotiations.

It is not entirely clear whether the other 26 works on the original 46-long roster will be affected, or will come home as agreed.

"If they want to give Italy back these works which they already agreed to return, let them," Rutelli said.

Italy has already begun putting on show archaeological finds recently returned to Italy after years in the US.

Earlier this year, Italy signed what some hope will be a groundbreaking deal with the Met. This envisages the return of artefacts in exchange for loans of equivalent value.

As well as the Met and the Getty, two other US museums with huge antiquities collections have come under the scrutiny of Italian investigators: Boston's Museum of Fine Arts and the Cleveland Museum of Art.

The Boston Museum has inked a similar deal to the Met's.

In November the Getty, reputedly the world's richest museum, returned three of 52 allegedly stolen Italian treasures it had acquired.

A former curator of the John Paul Getty Museum, Marion True, is on trial in Rome for allegedly acquiring stolen artefacts. It is the first such trial of an American museum curator.

Some of the works which the Getty was due to return were set to be exhibited as evidence in court.

The February 21 agreement with the Met ended a 25-year wrangle over disputed antiquities.

The objects included one of the Met's gems, a sixth-century BC painted vase called the Euphronios Krater.

It is widely regarded as one of the finest examples of its kind.

Italian art police presented the Met with strong evidence that the red and black terracotta vase, or calyx, was stolen from the Etruscan burial site of Cerveteri near Rome in the early '70s.

The agreement also covered four ancient vases from Apulia (present-day Puglia) and a large collection of silverware stolen from Morgantina.

The vases will come home shortly, the Krater by January 15 2008, and the silverware by January 15 2010.

In the meantime, in exchange for getting the long-sought pieces back, the Italian government will loan works of equivalent beauty and importance to the Met.

Met Director Philippe de Montebello has said he already has a "wish list" of loans.

In his talks with Rutelli on November 29, de Montebello is expected to go over some of the fine print of the February accord.

The Met deal and the True trial have signalled that Italy is getting serious about recovering lost artefacts.

By setting a precedent that could be used by other countries - notably Greece - Italy has sent alarm bells around the art world.

Rutelli reiterated on Thursday that "it is our government's duty to make it clear that all the world's museums which exhibit ransacked Italian works must return them". A 1970 UNESCO convention, which both Italy and the US have signed, bans the import, export and transfer of ownership of cultural property.