Washington DC - President Joe Biden has recognized the mass killings of Armenians by Ottoman Turks as "genocide," infuriating NATO ally Turkey in a move that is likely to further inflame Washington's tensions with Ankara.

"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.

"We honor their story. We see that pain. We affirm the history. We do this not to cast blame but to ensure that what happened is never repeated," he added.

Biden's move wasn't unexpected: As a presidential candidate, he had spoken about the "genocide" of Armenians at a remembrance day event.

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He had also announced a tougher course against Turkish President Recep Tayyip Erdoğan, whom he had described as an "autocrat."

In 2019, both chambers of the US Congress passed resolutions recognizing the Armenian genocide.

Erdoğan responded at the time by saying that "a country whose history is stained with genocide, slavery, and exploitation has no right to say anything to Turkey or teach Turkey a lesson."

Ties between Ankara and Washington have already been strained by a string of issues, including the US support to Syrian Kurdish militia and Turkey's purchase of Russian missile defense systems.

Biden's genocide recognition opens "a deep wound that undermines our mutual trust and friendship," the Turkish Foreign Ministry said, adding that Ankara rejects it as a "vulgar distortion of history."

"We reject and denounce in the strongest terms the statement of the President of the US regarding the events of 1915," the ministry said, charging that it "hinders" peace and stability in the region.

It is an extremely unfortunate and saddening day in terms of our bilateral ties [with the US]," Erdoğan's communications director Fahrettin Altun said, as quoted by state news agency Anadolu.

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Turkish Foreign Minister Mevlut Cavusoglu earlier wrote on Twitter that the classification was "based solely on populism" and "the greatest betrayal to peace and justice."

In a letter to the Armenian patriarch in Turkey ahead of Biden's statement, Erdoğan said he "remembers with respect the Ottoman Armenians we lost in World War I" and "shares sorrow" of the victims' relatives.

On April 24, 1915, thousands of Armenian intellectuals suspected of hostility towards Ottoman rule were rounded up.

Armenians were systematically persecuted and killed at the hands of the Ottomans in 1915 and 1916. According to estimates, up to 1.5 million Armenians lost their lives during that time.

Turkey vehemently rejects classifying the killings as genocide, saying that both Armenians and Turks were killed in civil strife that occurred when Armenians rose up against their Ottoman rulers and sided with invading Russian troops.

Commemorations of the killings were under way in Armenia and other countries too.

Armenian Prime Minister Nikol Pashinyan welcomed Biden's statement "with great enthusiasm" and spoke of "a powerful step on the path of truth and historical justice."

French President Emmanuel Macron marked a national day of remembrance by attending a ceremony at a memorial to the genocide in the center of Paris.

"The French people and the Armenian people are forever connected," the 43-year-old wrote on Twitter.