"This year we mark the centennial of the Meds Yeghern, the first mass atrocity of the 20th century," he said.
Despite pressure by Armenian lobbies', Obama preferred to call the events "Meds Yeghern" or "Great Calamity,” a term Armenians use for the relocation of Armenians by the Ottoman Empire due to security concerns during World War I.
"Beginning in 1915, the Armenian people of the Ottoman Empire were deported, massacred, and marched to their deaths. Their culture and heritage in their ancient homeland were erased. Amid horrific violence that saw suffering on all sides, one-and-a-half million Armenians perished," Obama said.
The American leader said that as relocation process unfolded, then U.S. ambassador Henry Morgenthau sounded the alarm inside the U.S. government and confronted Ottoman leaders.
He added that thanks to the efforts of those like Morgenthau "the truth of the Meds Yeghern emerged and came to influence the later work of human rights champions like Raphael Lemkin, who helped bring about the first United Nations human rights treaty."
"This centennial is a solemn moment. It calls on us to reflect on the importance of historical remembrance, and the difficult but necessary work of reckoning with the past," Obama said.
While campaigning for president in 2008, Obama promised to refer to the 1915 events as genocide but has thus far failed in that promise.
He said his views has not changed but suggested "a full, frank, and just acknowledgement of the facts is in all our interests."
He also welcomed Pope Francis' remarks calling the events "the first genocide of 20th century"
He also appreciated the efforts by Turkish and Armenian historians, and others who have sought to shed light that period of history.
The 1915 events took place during World War I when a portion of the Armenian population living in the Ottoman Empire sided with the invading Russians and revolted.
The relocation by the Ottomans of Armenians in eastern Anatolia following the revolts resulted in numerous casualties. Turkey does not dispute that there were casualties on both sides, but rejects the definition of "genocide."
Turkey, which does not dispute casualties among both Armenian and Turkish communities during World War I, has called for the establishment of a joint commission of historians and the opening of archives to study and uncover what happened between the Ottoman Empire and its Armenian citizens.