President Joe Biden on Saturday recognized the killing of 1.5 million Armenians by Ottoman Empire forces in the early 20th century as a genocide, a historic though largely symbolic move that will likely strain already fraught relations with Turkey.

Biden’s declaration is a major break from past U.S. administrations, which avoided calling the atrocities genocide due to concerns over alienating Turkey, an important NATO ally and influential power in the Middle East. Turkey has contested that the killings constitute a genocide.

“Each year on this day, we remember the lives of all those who died in the Ottoman-era Armenian genocide and recommit ourselves to preventing such an atrocity from ever again occurring,” Biden said in a statement on Armenian Genocide Remembrance Day.

As a candidate, Biden last year vowed to make this declaration, which is widely supported by human rights groups and Armenians. The Trump administration refrained from recognizing the events as a genocide, instead labeling them as “mass atrocities.”

Following the arrest of Armenian intellectuals and community leaders in Constantinople – now known as Istanbul – by Ottoman authorities, roughly 1.5 million Armenians were killed in the events known as Meds Yeghern that took place from 1915 – 1923.

“A world unstained by the daily evils of bigotry and intolerance, where human rights are respected, and where all people are able to pursue their lives in dignity and security,” Biden said. “Let us renew our shared resolve to prevent future atrocities from occurring anywhere in the world. And let us pursue healing and reconciliation for all the people of the world.”

The Turkey Ministry of Foreign Affairs said Saturday that the Biden administration’s statement would “open a deep wound that undermines our mutual trust and friendship.”

Biden and Turkish President Recep Tayyip Erdogan, in a phone call Friday, agreed to hold a bilateral meeting on the margins of the NATO Summit in June.

“It is an important day for all Armenians. Following the resolutions adopted by US Congress in 2019, President Biden honored the memory of victims of the Armenian Genocide,” Armenian Prime Minister Nikol Pashinyan wrote in a tweet on Saturday.

“The US has once again demonstrated its unwavering commitment to protecting human rights and universal values,” Pashinyan wrote.