France's Foreign Ministry said on Thursday that the sixth-century Hagia Sophia museum originally built as a Christian cathedral in Istanbul must remain open to all.

A Turkish court on Thursday heard a petition seeking to convert the Hagia Sophia, one of Turkey's most visited and beloved tourist sites, back into a mosque.

"A symbol of tolerance and diversity, this place must remain open to all," a French Foreign Ministry spokesman said.

France's appeal comes after the spiritual head of the world’s Orthodox Christians warned that converting Istanbul’s sixth century Hagia Sophia back into a mosque would sow division.

US Secretary of State Mike Pompeo also urged Turkish President Recep Tayyip Erdogan not to convert the Hagia Sophia into a mosque.

The Hagia Sophia is a UNESCO World Heritage Site that was at the core of both the Christian Byzantine and Muslim Ottoman empires, and is today one of Turkey's most visited monuments.