China's heritage authorities said Tuesday they had written to auction house Christie's in a bid to stop the sale of two looted bronze sculptures.

The State Administration of Cultural Heritage (SACH) sent the letter to the auction house on Feb. 17, but only announced it in a statement Tuesday.

"(In the letter) we requested they stop the auctions and hope the parties (to the auction) understand and respect this proper request from Chinese people," the statement said.

Christie's will auction the two bronze sculptures of the heads of a rabbit and a rat on Wednesday. They are expected to fetch between 16 million and 20 million euros (20.8 million to 26 million U.S. dollars).

A spokesman for the SACH said Christie's had replied to the letter, but he declined to discuss the content of the reply.

The statement said many people in China and abroad were working hard to return the sculptures to China and the SACH had voiced the widespread request of Chinese people. "The SACH will follow developments."

A group of 81 Chinese lawyers and three foreign lawyers were organizing a campaign to stop the auctions.

The Association for the Protection of Chinese Art in Europe (APACE) filed a motion at the Tribunal de Grande Instance in Paris on Thursday, seeking an injunction to stop the auction. The court rejected the motion Monday.

The heads were among 12 animal head sculptures that formed the zodiacal clepsydra decorating the Calm Sea Pavilion in the Old Summer Palace of Emperor Qianlong (1736-1795) in Beijing.

They were looted when the palace was burned down by Anglo-French allied forces during the Second Opium War in 1860.

"We believe there is a common understanding in the international community that looted cultural objects should be returned to their own countries. This is a basic cultural right of people in the origin countries," the SACH statement said.

Objects taken by foreign invaders since the 1860s, including many valuable objects from the Old Summer Palace, should be returned to China, it said. "The Chinese government is strongly against auctioning these cultural heritage items."

Meanwhile, the Chinese lawyers would "make every effort" to halt the auction at the Christie's, said Li Xingfeng, a member of the group of lawyers, in Beijing. But he refused to elaborate on what they would do.

"If they were sold, we would start legal proceedings against the buyer," he said.

"We hope to raise public attention in Europe to the fate of numerous Chinese works stolen in the past," Ren Xiaohong, one of the group and representing the APACE in Paris, said Monday.