ANKARA — With President Recep Tayyip Erdogan holding huge sway over his country’s judiciary, Turkey’s highest administrative court will decide whether to approve his plan to turn the revered ancient Aghia Sophia cathedral into a mosque.

The Council of State got the case July 1 and is expected to make a ruling by July 16, said Reuters and the Greek newspaper Kathimerini, after the judges concluded a quick hearing.

Already increasing tensions with Greece by saying Turkish drill ships would hunt for energy off Crete, Erdogan wants to change the status of Hagia Sophia, now a museum and a UNESCO World Heritage Site.

Ecumenical Patriarch Vartholomaios, the spiritual head of some 300 million Orthodox Christians worldwide and based in Constantinople where the Orthodox church stands, said making it a mosque would disappoint Christians and “fracture” East and West, setting up a potential clash of religions.

Hagia Sophia, which has minarets around it, was converted into a mosque when the city fell to the Ottoman invaders in 1453 but became a museum in 1934 under the rule of Mustafa Kemal Ataturk, founder of the modern Turkish state.

“The potential conversion of Hagia Sophia into a mosque will turn millions of Christians around the world against Islam,” Vartholomaios warned. “We hope that wisdom and reason ultimately prevail,” he added, the report said.

He called on Turks to support keeping the cathedral as a museum as it is now designated, saying it brings together people and cultures from all over the world, the site one of the most popular in the city, drawing about three millions tourists annually.

U.S. Secretary of State Mike Pompeo jumped into the fray despite President Donald Trump's affinity for Erdogan – who regularly calls the US leader on the phone and is said to get some favors from him.

Pompeo said Turkey should leave Hagia Sophia as it is, putting out a statement the US urged Erdogan to back off and keep the cathedral “as an exemplar of its commitment to respect the faith traditions and diverse history that contributed to the Republic of Turkey, and to ensure it remains accessible to all."

Turkish groups have campaigned for years for Hagia Sophia’s conversion into a mosque and how a champion in Erdogan, a pious Muslim, who ahead of local elections last year said he would do it.

Many Turks argue that mosque status would better reflect the identity of Turkey as an overwhelmingly Muslim country, and recent polls have shown that most Turks support a change although it could further deteriorate frayed relations with Greece which at times have approached near-conflict points.