Washington (CNN) The Senate on Thursday passed a resolution formally recognizing the mass killings of Armenians from 1915 to 1923 as genocide, a move the Turkish government has long opposed.

The resolution states, "it is the policy of the United States to commemorate the Armenian Genocide through official recognition and remembrance," describing the genocide as "the killing of an estimated 1,500,000 Armenians by the Ottoman Empire from 1915 to 1923."

It passed by unanimous consent after Sen. Bob Menendez of New Jersey, the top Democrat on the Senate Foreign Relations Committee, brought it up for consideration on the floor. Under Senate rules, legislation can pass by unanimous consent without a roll call vote as long as no senator objects.

The designation as a genocide by Congress is a significant political development as Turkey maintains to this day the killings did not constitute genocide and disputes the death toll, putting the figure closer to 300,000.

Turkish presidential spokesperson Fahrettin Altun tweeted after the vote "The behavior of some members of the U.S. Congress is damaging the Turkish-American ties."

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