President Joe Biden characterized the Ottoman Empire’s mass killings of Armenians over a century ago as genocide on Saturday, drawing applause from Armenian groups yet risking deteriorating ties with US ally Turkey, which opposes the label of genocide.

Biden used the word “genocide” in a speech commemorating Armenian Remembrance Day, defying decades of US presidents who have denied using the term to refer to the Ottoman Empire’s expulsion and murder of about 1.5 million Armenians (Now known as Turkey).

On the campaign trail last year, the president alluded to it as genocide, and he pledged to do so if elected, a statement supported by many representatives of Congress from both parties.

Earlier this week, Biden reportedly cautioned Turkey about his move during a phone call with President Recep Tayyip Erdogan, who has rejected genocide and also claimed Armenian deportation was fair.

President Biden wrote on Saturday that on this day each year, we commemorate the lives of the people who died in the genocide of Armenians and renew our commitment to keeping such atrocities from happening again.

In 1915, during World War I, the Ottoman Empire’s impending dissolution forcefully evacuated Armenians from eastern Anatolia to Syria, where it was feared they would assist Russian troops. The majority of historians argued that it was a concerted effort at ethnic cleansing motivated by imperialism, but Turkey has refuted this view, arguing that the killings were not intentional and the deportations were necessary for security reasons.

Numerous other countries have publicly designated the atrocities as genocide, but the US has refrained from doing so in order to prevent antagonizing Turkey, a NATO participant, and long-standing US security partner. However, links between the United States and Turkey have steadily deteriorated in recent years as the two countries’ priorities collide and Turkey strengthens ties with Russia, potentially rendering Biden’s monumental move less expensive.

Turkey cautioned earlier this week that if Biden uses the term “genocide,” bilateral ties could deteriorate. Mevlut Cavusoglu, Turkish Foreign Minister, has said that If the US wishes to deteriorate ties, it is their option.