Pope Francis will hold a mass commemorating the centennial  of the Armenian genocide this Sunday, in what will be one of the most high-profile recent acknowledgments of the historic atrocity by a major world leader. Ahead of the mass, Francis lamented the lack of consensus on recognizing the early 20th century mass killings during a meeting Thursday with Armenian bishops.

The Sunday mass will be held 12 days before the official commemoration of the genocide’s centennial on April 24. Francis expressed his hopes that the occasion would help “to hasten concrete gestures of reconciliation and peace among the nations that have not yet reached a consensus on the reading of such sorrowful events,” in a statement reported by Vatican Radio.

An estimated 1.5 million Armenians died after Turks, during the Ottoman Empire, began forcibly evacuating ethnic minorities in what is present-day Turkey in 1915. The evacuation campaign is thought to have wiped out more than half of the Armenian population at the time and is widely acknowledged as the first genocide of the 20th century. The Turkish government has strongly rejected this view, arguing that the number of deaths was inflated and the result of unrest, disease and famine rather than a deliberate campaign of annihilation.

Acknowledgment of the historic tragedy by public figures around the world has always been a sensitive undertaking, as they are invariably met by vocal objections from the Turkish government. As a result, only a handful of countries officially recognize the atrocity as a genocide, a word most world leaders steer clear of when discussing the issue. Ahead of his election to office, President Barack Obama notably vowed to use the word when describing the killings but has yet to live up to the campaign promise. Turkey is a NATO member and an important ally straddling Europe and the Middle East.

Francis himself is no stranger to the controversy, but unlike most other world leaders, the pontiff has not shied away from publicly characterizing the killings as a genocide. As a cardinal in Argentina, Francis led a service of remembrance in Buenos Aires on the 91st anniversary of the genocide in 2006, during which he called the killings the “gravest crime of Ottoman Turkey.” Francis’ homeland of Argentina has significant Armenian and Greek minorities, whose ancestors migrated from the Ottoman Empire in the wake of World War I.

In 2013, the newly elected pope provoked a diplomatic rebuke from Ankara after he told a visiting delegation of Armenian Christians that the massacre of Armenians by the Ottomans was “the first genocide of the 20th century.” The comments were welcomed by prominent Armenians around the world, with the director of the Armenian National Committee of South America, Alfonso Tabakian, calling them a “very important” step, as the first such statement from the Catholic leader since his elevation to the papacy, and a sign that “more states, parliaments and international organizations are adopting this position against the denial of history perpetrated by the Turkish State.”

The pope’s April 12 commemoration is just as likely to produce the same polarized dynamic among the Turkish government, Armenians and other supporters of genocide recognition. The ecumenical ceremony, which falls on the Catholic observance of Divine Mercy Sunday,  will include representatives of Armenia’s various Christian communities as well as Armenian President Serzh Sarkisian. The vast majority of Armenian Christians follow the country’s Eastern Orthodox Apostolic Church, although more than 350,000 are members of the Armenian Catholic Church.