WASHINGTON (Reuters) - The Trump administration on Tuesday refrained from endorsing a resolution passed by the U.S. Senate recognizing as a genocide the mass killings of Armenians a century ago, saying it continued to see them as “mass atrocities.”

The position taken appears aimed at assuaging Turkey, which was infuriated by the passage of the measure last week. The measure is non-binding but asserts that it is U.S. policy to commemorate as genocide the killing of 1.5 million Armenians by the Ottoman Empire from 1915 to 1923.

In response, Turkey summoned the U.S. Ambassador to Ankara to convey its dismay. The NATO allies had already been at loggerheads over some issues, ranging from Turkey’s purchase of a Russian missile defense system to policy on the war in Syria.

U.S. President Donald Trump has been criticized by U.S. lawmakers, including his fellow Republicans, for shielding Turkish President Tayyip Erdogan, with whom he enjoys a special rapport, from U.S. sanctions over the weapons purchase.

“The position of the Administration has not changed,” State Department spokeswoman Morgan Ortagus said in a statement on the subject of Armenia. “Our views are reflected in the President’s definitive statement on this issue from last April.”

On the April 24 Armenian Genocide Remembrance Day, Trump in a statement commemorated the killings, describing them as “mass atrocities” as opposed to a genocide.

“Beginning in 1915, one and a half million Armenians were deported, massacred, or marched to their deaths in the final years of the Ottoman Empire,” he said.

Turkey accepts that many Armenians living in the Ottoman Empire were killed in clashes with Ottoman forces during World War One, but contests the figures and denies that the killings were systematically orchestrated and constitute a genocide.

For decades, measures recognizing the Armenian genocide have stalled in the U.S. Congress, stymied by concerns about relations with Turkey and intense lobbying by Ankara. The passing of the resolution highlights the bipartisan anger of the U.S. Congress toward Ankara over its recent actions.