The US House of Representatives has voted overwhelmingly in favour of recognising the mass killing of Armenians by Ottoman Turks during World War One as “genocide”.
The issue is highly sensitive and comes at a time of difficult bilateral relations with Turkey.
Presidential hopeful Joe Biden said the vote honoured the memory of victims.
But Turkey’s foreign minister said the vote was in revenge for its military offensive in northern Syria.
The House also voted overwhelmingly to call on President Donald Trump to impose sanctions on Turkey and some of its officials over the offensive.
How did the House vote?
The resolution passed by a vote of 405 to 11.
House Speaker Nancy Pelosi joined her colleagues “in solemn remembrance of one of the great atrocities of the 20th Century”.
Mr Biden tweeted: “By acknowledging this genocide we honour the memory of its victims and vow: never again.”
Chairman of the House’s Intelligence Committee, Adam Schiff, tweeted: “The House just voted to recognize the Armenian Genocide – a vote I fought for 19 years to make possible, that tens of thousands of my Armenian American constituents have waited decades to see. We will not be party to genocide denial. We will not be silent. We will never forget.
How has Turkey reacted?
It has strongly condemned the move. Foreign Minister Mevlut Cavusoglu called the vote “null and void”, linking it to Turkey’s military offensive against Kurdish fighters in northern Syria whom it regards as terrorists. Kurdish troops have been allied to the US in fighting the Islamic State (IS) group.
Mr Cavusoglu tweeted: “Those whose projects were frustrated turn to antiquated resolutions. Circles believing that they will take revenge this way are mistaken. This shameful decision of those exploiting history in politics is null and void for our Government and people.”
Turkey denies that there was a systematic campaign to slaughter Armenians as an ethnic group during World War One.
There is general agreement that hundreds of thousands of Armenians died when the Ottoman Turks deported them en masse from eastern Anatolia to the Syrian desert and elsewhere in 1915-16. They were killed or died from starvation or disease.
The total number of Armenian dead is disputed. Armenians say 1.5 million died. The Republic of Turkey estimates the total to be 300,000. According to the International Association of Genocide Scholars (IAGS), the death toll was “more than a million”.
The dispute about whether it was genocide centres on the question of premeditation – the degree to which the killings were orchestrated. Many historians, governments and the Armenian people believe that they were; but a number of scholars question this.
Turkish officials accept that atrocities were committed but argue that there was no systematic attempt to destroy the Christian Armenian people. Turkey says many innocent Muslim Turks also died in the turmoil of war.