(nytimes.com) WASHINGTON — President Obama declined on Friday to refer to the 1915 massacre of Armenians as genocide, breaking a campaign promise as his presidency nears its end.

Mr. Obama, in a statement to mark Armenian Remembrance Day on April 24, called the massacre the first mass atrocity of the 20th century and a tragedy that must not be repeated. Yet he stopped short of using the word genocide, a term he applied to the killings before he became president in 2009.

“I have consistently stated my own view of what occurred in 1915, and my view has not changed,” Mr. Obama said.

Armenian-American leaders have urged Mr. Obama each year to keep a pledge he made as a presidential candidate in 2008, when he said the United States government had a responsibility to recognize the attacks as genocide and vowed to do so if elected. Mr. Obama’s failure to fulfill that pledge in his final annual statement on the massacre infuriated advocates and lawmakers who accused the president of outsourcing America’s moral voice to Turkey, which staunchly opposes the genocide label.

“It’s a Turkish government veto over U.S. policy on the Armenian genocide,” Aram Hamparian, head of the Armenian National Committee of America, said in an interview. Referring to President Recep Tayyip Erdogan of Turkey, Mr. Hamparian said “it’s like Erdogan imposing a gag rule very publicly and an American president enforcing that gag rule.”

Historians estimate that as many as 1.5 million Armenians were killed by Ottoman Turks in an episode widely viewed by scholars as genocide. Turkey, a United States partner and NATO ally, denies that the killings constituted genocide and says the death toll has been inflated.

How #Turkish Dictator SILENCED most powerfull country in the world #USA to deny #ArmenianGenocide #Obama the coward pic.twitter.com/ggNbnbvNN3

— Wally Sarkeesian (@gagrulenet) April 24, 2016

Though Obama administration officials have debated using the genocide label in the past, this year’s deliberations come as Mr. Obama seeks Turkey’s assistance in fighting the Islamic State — especially along Turkey’s border with Syria. The United States and its European partners are also counting on Mr. Erdogan to help stem the influx of migrants to Europe.

If Mr. Obama felt pressure not to offend Turkey, he was not alone among world leaders. Chancellor Angela Merkel of Germany has faced intense criticism for allowing the possible prosecution of a television satirist for reciting an intentionally offensive poem about Mr. Erdogan.

Mr. Hamparian said officials from the White House’s National Security Council and the Atrocities Prevention Board that Mr. Obama established told him on Thursday that labeling the killings as genocide would introduce uncertainty in the region during a time when Turkey is playing an important role in a number of matters. He said it was hypocritical for Mr. Obama to call every year for “a full, frank, and just acknowledgment of the facts” while refusing to acknowledge them himself. “It’s like, ‘You should do this, but I won’t,’ ” Mr. Hamparian said.

Mr. Obama’s calls for transparency about the massacre played a prominent role in his presidential campaign, held up by him as an example of the type of sorely needed straight talk about foreign affairs and historical events. Samantha Power, one of his campaign surrogates and now his United Nations ambassador, issued a roughly five-minute video imploring Armenian-Americans to vote for Mr. Obama precisely because he would follow through on his promise.

Representative Adam Schiff of California, the top Democrat on the House Intelligence Committee, said he was “gravely disappointed” that Mr. Obama would leave office with the campaign pledge unfulfilled. Mr. Schiff has introduced legislation calling on the president to urge Turkey to fully acknowledge the genocide.

“Remaining silent in an effort to curry favor with Turkey is as morally indefensible as it will be ineffectual,” Mr. Schiff said.

The White House issued Mr. Obama’s annual statement on the massacre while the president was in London but declined to comment on the matter.