Muslim Congresswoman Ilhan Omar on Tuesday defended her decision to oppose a U.S. House resolution recognizing 1915 events as "genocide" against Armenians.

The U.S. first needs to worry about "earlier mass slaughters" including "the transatlantic slave trade and Native American genocide," Rep. Omar of Minnesota said in a statement late Tuesday.

These "historical crimes against humanity... took the lives of hundreds of millions of indigenous people," she added.

According to Ward Churchill, a professor of ethnic studies at the University of Colorado, the reduction of the North American Indian population from an estimated 12 million in 1500 to barely 237,000 in 1900 represents a "vast genocide... the most sustained on record."

David E. Stannard, a historian at the University of Hawaii, said Native Americans had undergone the "worst human holocaust the world had ever witnessed... consuming the lives of countless tens of millions of people."

During the adoption of the resolution, Omar voted "present," along with Rep. Eddie Bernice Johnson of Texas and Rep. Paul Gosar of Arizona.

She stressed that "recognition of genocide should not be used as cudgel in a political fight."

"It should be done based on academic consensus outside the push and pull of geopolitics," Omar added.

The House’s move is seen as a clear rebuke to NATO ally Turkey in the wake of its anti-terror operation in northern Syria.

Turkish officials have condemned the House resolution, while Turkish Foreign Ministry summoned U.S. Ambassador David Satterfield to express Ankara’s strong opposition to the bill.

Turkey objects to the presentation of the 1915 incidents as a "genocide," rather calling them a tragedy in which both Turks and Armenians suffered casualties in the heat of World War I.

Ankara has repeatedly proposed the creation of a joint commission of historians from Turkey and Armenia under the supervision of international experts to examine the issue.