Italy said on Wednesday it was ready to break off ties with the J. Paul Getty Museum in Los Angeles unless it agrees quickly to return art works that Rome says were looted.
Culture Minister Francesco Rutelli said he was tired of stop-go talks and was making a final call to the Getty, one of the world's richest museums.
"Either there is an agreement or there is a breakdown," he told reporters in Rome. "The time has passed when people could turn a blind eye to looting."
Getty director Michael Brand told Rutelli last month that his museum would return 26 of 46 pieces that Italy wants back.
Rutelli, showing photographs he said proved the works were looted, reiterated that the offer was unacceptable. "That would be saying 'yes' to international trafficking," he said.
Rome has insisted the Getty return a prized bronze sculpture called the "Statue of a Victorious Youth" and a limestone and marble statue of the Greek goddess Aphrodite.
In its letter last month, the Getty said it would not hand over the 2,500-year-old sculpture because it was found in international waters in 1964. The museum said evidence on the Aphrodite piece was inconclusive.
Rutelli did not say what measures he might take if the Getty did not agree to Rome's demands. Maurizio Fiorilli, a lawyer representing the Culture Ministry, said a complete break with the Getty would probably put an end to joint scientific work, scholarships and Italian loans of art work to the museum.
A cut-off could hurt Italy more than the Getty, which since the 1980s has lent Italy more than 80 objects, twice as many as Italy has sent to the museum.
The Getty case is complicated by the trial in Rome of former curator Marion True, accused of conspiracy in trafficking stolen Italian antiquities. A Greek prosecutor has charged True with illegally buying a 4th-century golden wreath smuggled out of Greece 13 years ago. True has denied any wrongdoing.
Italy's campaign to recover looted antiquities has led to agreements with other U.S. institutions such as the Metropolitan Museum of Art in New York and the Boston Museum of Fine Arts.