With Turkish President Recep Tayyip Erdogan saying he plans to turn the revered Greek Orthodox Aghia Sophia cathedral in Constantinople into a mosque after March 31 elections, The United Nation’s cultural arm, UNESCO, said changing the World Heritage site’s status would require approval by the Paris-based organization.

Undeterred, Erdogan took another shot at Greece – at the same time he’s been sending fighter jets into Greek airspace – and said that “Constantinople will never exist again.” “The name of this area is Islambol (full of Islam) and you know that,” staying defiant.

The 6th Century Aghia Sophia is now a museum and was the main seat of the Greek Orthodox Church before it was initially turned into a mosque following the Ottoman conquest of Istanbul – then Constantinople – in 1453. It became a museum in 1935.

Greeks still refer to the city as Constantinople, 566 years after the conquest.

Erdogan said he wants to convert the church as a response to US President Donald Trump’s decision to recognize the Golan Heights which Israel gained in 1967 from Syria as Israeli territory and said rising tensions are because of political instability in Greece.

Erdogan’s renewed mulling of turning the revered Orthodox cathedral of Aghia Sophia in Constantinople into a mosque, and renaming it, has drawn the ire of the Greek government.

Erdogan indicated that it was possible to “change its name from museum to Hagia Sophia Mosque,” an idea he has suggested before as he pushed Greece to give more rights to Turkish Muslims living in the northern part of that country near the Turkish border.

There have been increasing calls for the government to convert the symbolic structure back into a mosque, especially in the wake of reports that the gunman who killed Muslim worshippers in New Zealand left a manifesto saying the Hagia Sophia should be “free of minarets.”