"The public sale is by definition transparent, it is subject to a level of requirement such that embassies would view them as a great tool for positive communication and cultural influence," Millon wrote.
Mexico says some of the artifacts are fakes and others should be returned to Mexico because they form part of the country's cultural heritage. The collection includes clay fertility figurines, pottery, jewelry and other items. A French couple started the collection in the 1960s.
Mexico passed a law in 1972 prohibiting the export of such artifacts. It's unclear if the relics were taken from Mexico before then. Mexico's ambassador to France, Juan Gomez Robledo, said he would personally go to the Paris auction in a last-minute appeal to try to stop it.
"We have run into the auction house's categorical refusal to stop this sale," Gomez Robledo said, adding he had appealed through legal and diplomatic channels in France to prevent the auction. Gomez Robledo wrote, "We will take the necessary actions to stop this sale."