ISTANBUL (CNA) -- The U.S. Conference of Catholic Bishops said Tuesday that July 24 “is a Day of Mourning” for Hagia Sophia. The former church and museum in Istanbul will that day be inaugurated as a mosque.

In a July 21 tweet, the USCCB said that it joins the Greek Orthodox Archdiocese of America “in offering our prayers for the restoration of Hagia Sophia as a place of prayer and reflection for all peoples.”

Turkish president Recep Tayyip Erdoğan signed a decree July 10 converting Hagia Sophia into a mosque. The decree followed closely on a ruling by the Council of State, Turkey's highest administrative court, which declared unlawful an 80-year old government decree which converted the building from a mosque into a museum.

Hagia Sophia was built in 537 under the Byzantine Emperor Justinian I as the cathedral of the Ecumenical Patriarchate of Constantinople. After the Ottoman capture of Constantinople in 1453, the basilica was converted into a mosque. Under the Ottomans, architects added minarets and buttresses to preserve the building, but the mosaics showing Christian imagery were whitewashed and covered.

In 1934, under a secularist Turkish government, the mosque was turned into a museum. Some mosaics were uncovered, including depictions of Christ, the Virgin Mary, John the Baptist, Justinian I, and Zoe Porhyrogenita. It was declared a World Heritage Site under UNESCO, the United Nations Educational, Scientific and Cultural Organization, in 1985.

As a mosque, the mosaics in Hagia Sophia will have to be covered during prayers, as will as the seraph figures located in the dome.

The members of the eparchial synod of the Greek Orthodox Archdiocese of America wrote July 19 that considering the inagauration of Hagia Sophia as a mosque, which they called a “program of cultural and spiritual misappropriation and a violation of all standards of religious harmony and mutual respect, we call upon all the beloved faithful of our Holy Archdiocese to observe this day as a day of mourning and of manifest grief. We urge you to invite your fellow Orthodox Christians and indeed all Christians and people of goodwill to share in the following observances.”

The observences are “that every Church toll its bells in lamentation on this day. We call for every flag of every kind that is raised on the Church property be lowered to half-mast on this day. And we enjoin every Church in our Holy Archdiocese to chant the Akathist Hymn in the evening of this day, just as we chant it on the Fifth Friday of the Great and Holy Fast.”

“Let us, in this time of grief and mourning, appeal to the Most Holy Theotokos and Ever-Virgin Mary,” the Greek Orthodox bishops wrote. “She is the 'only Hope of the hopeless', and as we chant to Her in the Akathist, 'the Repository of the Wisdom of God, the Treasury of His Foreknowledge'.”

The Greek Orthodox bishops concluded: “Therefore, with complete faith in the Foreknowledge of our Trinitarian God, and in the Divine Plan for our salvation, we entrust the future of our beloved [Hagia Sophia] to His Wisdom, and we supplicate She who is the very Treasury of that Knowledge and the Repository of that Wisdom to intercede for us, to comfort us, to give us Her strength, and to manifest to us Her counsel, that we may ever do and say that which is pleasing in the sight and in the hearing of Her Son, our Lord, God, and Savior Jesus Christ, to the glory of God the Father, Who together with the Holy Spirit is worshipped One God, unto the ages of ages. Amen!”

Dr. Elizabeth Prodromou, director of the Initiative on Religion, Law, and Diplomacy at the Fletcher School of Law and Diplomacy at Tufts University, told CNA last week that the July 24 date for the inauguration of Hagia Sophia as a mosque is “rife with symbolism.”

The day is the anniversary of the Treaty of Lausanne, signed in 1923 after the defeat of the Ottoman Empire in World War I, which established the borders of the modern Turkish state and included explicit protections for Christian minorities there.

Erdoğan “has stated indirectly – and increasingly, directly – that he sees Lausanne as something that should be abrogated,” Prodromou said. It’s also a signal to Turkey’s NATO allies and fellow countries that it “is not interested in continuing within the context of treaties that are meant to provide stability and order in the region.”

Archbishop José Gomez of Los Angeles and Bishop Joseph Bambera of Scranton, the US bishops' president and ecumenical chair, respectively, said July 14 that “we join Pope Francis and our Orthodox Christian brothers and sisters in expressing deep sadness over the decree by Turkey’s president to open Hagia Sophia as a mosque.”

“For many years now, this beautiful and cherished site has served as a museum where people of all faiths can come to experience the sublime presence of God. It has also stood as a sign of good will and peaceful coexistence between Christians and Muslims and an expression of humanity’s longings for unity and love.”

Edward Clancy, director of outreach for Aid to the Church in Need-USA, said July 17 that the 1934 decision to secularize Hagia Sophia, “which also allowed for the restoration of Christian iconography plastered over by Ottoman authorities – made it a symbol of inter-religious harmony, a place where Islamic and Christian heritages could meet in peace. The loss of that privileged place of inter-religious encounter is incalculable.”

“Hagia Sophia has held the promise of peaceful coexistence between Christians and Muslims, an acknowledgement of humanity’s yearning for unity and love. Turning Hagia Sophia into a mosque also sends a painful message to Christians throughout the Middle East who have suffered persecution and cultural cleansing at the hands of ISIS and other Islamist groups,” Clancy continued.

He said the decision to convert the building into a mosque “reflects Turkey’s ambition to recapture Ottoman glory and power in the region, an aggressive posture evident in the country’s military incursions into Syria and Iraq and bound to further destabilize an already volatile region that remains a battlefield of political interests and religious values.”

In November 2019, the Council of State ruled that Chora Church, another Istanbul museum that was built as a church and was later made a mosque, should be converted back into a mosque. Despite this, the city's official museum tourism website continues to feature Chora Church as one of its destinations.