Converting Istanbul’s sixth century Hagia Sophia back into a mosque would sow division, the spiritual head of the world’s Orthodox Christians warned on Tuesday, ahead of a Turkish court ruling on a building that has been a museum since 1934, Reuters reports.

The court is set to rule on July 2 on a challenge to its current status that disputes the legality of its conversion into a museum in 1934 in the early years of the modern secular Turkish state founded by Mustafa Kemal Ataturk.

“The conversion of Hagia Sophia into a mosque will disappoint millions of Christians around the world,” said Ecumenical Patriarch Bartholomew, the spiritual head of some 300 million Orthodox Christians worldwide. He is based in Istanbul.

Changing its status will “fracture these two worlds” at a time when mankind needs unity more than ever because of the COVID-19 pandemic, Bartholomew said.