TEHRAN -- Former Iranian president Mohammad Khatami in his Monday’s visit to Chicago’s Oriental Institute Museum said Iran’s clay tablets kept there should not fall victim to political games.

Head of the International Center for Dialogue among Civilizations underlining Iran’s cultural rights and ownership of the artifacts added, “The heritage of mankind is not tradable and replaceable. “The artifacts do not belong to the governments. They belong to the whole Iranian nation and the entire world. We must stand up to the ongoing propaganda and safeguard the historical assets of Iran which are held in trust in this university and museum.”

The Oriental Institute Museum curator Gil Stein pointed to the long process of deciphering the tablets, expressing hope the process will be over soon and the artifacts will return home.

The clay tablets have been kept in the University of Chicago's Oriental Institute since the 1930s. But lawyers for Americans wounded in a 1997 bombing in Jerusalem claimed to seize the collection as part of Iranian assets in the United States.

The tablets date from the Achaemenid Era, 553 BC-330 BC and were excavated from Persepolis, the ancient Persian capital built by Darius I.