Turkey's highest administrative court has been advised to reject a request that Istanbul's Hagia Sophia be turned back into a mosque, according to state-run media.
The sixth-century structure was the Byzantine Empire's main cathedral before it was changed into an imperial mosque following the Ottoman conquest of Istanbul.
Mustafa Kemal Ataturk, the founder of the modern Turkish republic, then turned it into a museum that attracts millions of tourists each year.
Nationalist and religious groups have long been pressing for the landmark, which they regard as a Muslim Ottoman legacy, to be converted back into a mosque. Others believe the Unesco World Heritage site should remain a museum, as a symbol of Christian and Muslim solidarity.
Turkey's Council of State began considering a request by a group that wants Hagia Sophia to revert back into a mosque.
The lawyer of the group argued that the building was the personal property of Ottoman Sultan Mehmet II, who conquered Istanbul, and pressed for the annulment of a 1934 Council of Ministers' decision that turned it into a museum, the Anadolu Agency reported.
A state lawyer, meanwhile, argued that the 1934 decision was legal, Anadolu reported. He recommended the request be rejected, arguing that a decision on restoring the structure's Islamic heritage was up to the government, the agency said.
A decision is expected within two weeks.
Greece as well as the Istanbul-based Ecumenical Patriarch Bartholomew I, considered the spiritual leader of the world's Orthodox Christians, have urged Turkey to keep Hagia Sophia as a museum. Bartholomew warned this week that its conversion into a mosque "will turn millions of Christians across the world against Islam".
US secretary of state Mike Pompeo waded into the debate on Wednesday, urging Turkey to keep Hagia Sophia as a museum "to serve humanity as a much-needed bridge between those of differing faith traditions and cultures".
His comments sparked a rebuke from Turkey's Foreign Ministry, which said Hagia Sophia was a domestic issue of Turkish national sovereignty.
Built under Byzantine Emperor Justinian, Hagia Sophia was the main seat of the Eastern Orthodox church for centuries, where emperors were crowned amidst ornate marble and mosaic decorations.
Four minarets were added to the structure with cascading domes and the building was turned into an imperial mosque following the 1453 Ottoman conquest of Constantinople - the city that is now Istanbul.
The building opened its doors as a museum in 1935, a year after the Council of Ministers' decision.