Greek officials have publicly presented no evidence that a controversial ancient bronze statue of Apollo bought in 2004 by the Cleveland Museum of Art was looted from Greece or any other country. Nor have they launched a claim to have the Apollo returned.

But according to the Louvre Museum in Paris, officials from the Hellenic Ministry of Culture threatened to withdraw the loan of 19 antiquities from an upcoming exhibition on the work of the great ancient Greek sculptor Praxiteles unless the Louvre agreed not to exhibit the Apollo.

"Greece made the withdrawal of the Apollo of Cleveland a condition sine qua non of its participation and therefore its loans to the Praxiteles exhibition," the Louvre said in a statement Friday. "The Louvre had no other choice but to withdraw its request" to borrow the sculpture from Cleveland.

The Louvre account, which differs in details from statements offered by Greek cultural officials, nevertheless shows how the Cleveland Apollo has become a focal point of the latest effort by Greece to halt the illegal trade in looted antiquities.

Malcolm Bell III, an art historian at the University of Virginia and a leading figure in the international debate over looted antiquities, said that Greece's action regarding the Apollo "is a warning that unprovenanced antiquities should not be purchased. I admire them for taking that position."

Timothy Rub, director of the Cleveland museum, said the institution has always acknowledged that the Apollo has gaps in its provenance, or ownership history. But he said it was wrong for Greece to raise its objections with the Louvre rather than by contacting the Cleveland museum directly.

In December, an unnamed source from the Hellenic Ministry of Culture told Agence France Presse that the Cleveland Apollo "was probably sold illegally after it was found in the 1990s by an Italian vessel in international waters between Italy and Greece."

Rub has said the Cleveland museum's research shows the Apollo did not come from the sea, and that "to have someone object to its inclusion in exhibition on basis of an unsubstantiated report is unfair."

Until recently, Greece, Italy and other countries rich in ancient treasures have asked museums in Europe and America to return antiquities when they had proof that they had been looted.

Soon, in fact, the Cleveland Museum of Art will send a delegation to Rome to discuss an Italian claim that objects in the museum's collection were looted.

Greece, however, took a harder line when it objected to a plan by the Louvre to exhibit the Cleveland museum's Apollo at an exhibit starting March 23.

Maria Volioti, an archaeologist in the Greek culture ministry, said Thursday that Greece objected to the loan of the Apollo because of the gaps in its provenance, which raise the possibility that it may have been looted. She also said that the objections to the Louvre were stated gently and were not meant, in her words, to "threaten" or "blackmail."

The Louvre, however, said that Greece delivered its ultimatum over the Apollo in the strongest possible terms, in writing and in person during a meeting in Athens in January.

The Cleveland museum bought the Apollo in 2004 from Phoenix Ancient Art, whose principals, brothers Ali and Hicham Aboutaam, have run afoul of authorities in the United States and Egypt.

But the museum bought the Apollo only after scientific evidence showed that the sculpture was excavated more than a century ago, and hence was not subject to recent laws aimed at halting trafficking in looted antiquities. Furthermore, the museum says it has a written statement from a German lawyer saying the Apollo was in his family's collection in the early 20th century.

Rub and other Cleveland museum officials have said it's better to buy, study and exhibit works such as the Apollo than to let them disappear into private hands, perhaps forever.

The Louvre has signed a 1970 UNESCO convention aimed at halting the illegal trade in looted antiquities, but it considered the Cleveland Apollo worthy of exhibiting.

Not being able to show the work "constitutes a major harm to the scientific community, which is losing a unique opportunity to evaluate this piece in connection with other works presented in this section of the exhibition," the Louvre statement said.