WASHINGTON — More than a century after the Ottoman Empire’s killing of an estimated 1.5 million Armenian civilians, President Biden is preparing to declare that the atrocities were an act of genocide, according to officials familiar with the internal debate. The action would signal that the American commitment to human rights outweighs the risk of further fraying the U.S. alliance with Turkey

Mr. Biden is expected to announce the symbolic designation on Saturday, the 106th anniversary of the beginning of what historians call a yearslong and systematic death march that the predecessors of modern Turkey started during World War I. He would be the first sitting American president to do so, although Ronald Reagan made a glancing reference to the Armenian genocide in a 1981 written statement about the Holocaust, and both the House and the Senate approved measures in 2019 to make its recognition a formal matter of U.S. foreign policy.

At least 29 other countries have taken similar steps — mostly in Europe and the Americas, but also Russia and Syria, Turkey’s political adversaries.

A U.S. official with knowledge of the administration’s discussions said Mr. Biden had decided to issue the declaration, and others across the government and in foreign embassies said it was widely expected.

Jen Psaki, the White House press secretary, declined to comment on Wednesday except to note that the administration would have “more to say” on the topic on Saturday.

Foreign Minister Ara Aivazian of Armenia said in an interview on Wednesday that “the recognition by the United States will be a kind of moral beacon to many countries.”

“This is not about Armenia and Turkey,” Mr. Aivazian said. “This is about our obligation to recognize and condemn the past, present and future genocide.”

The designation and whether Mr. Biden would issue it have been seen as an early test of his administration’s dealings with the government of President Recep Tayyip Erdogan of Turkey.

The two men have had a somewhat testy relationship in the past, in contrast to the generally warm treatment Mr. Erdogan received from President Donald J. Trump, and the genocide declaration could prompt a backlash from Turkey that risks its cooperation in regional military conflicts or diplomatic efforts. Past American presidents have held back from the declaration for that very reason, and Mr. Biden could still change his mind about issuing it.

While Turkey agrees that World War I-era fighting between the Muslim Ottomans and Christian Armenians resulted in widespread deaths, its leaders have resolutely rejected that the killing campaign that began in 1915 amounted to genocide.

Yet Turkish officials have been bracing for the genocide declaration ever since Mr. Biden committed to it during his presidential campaign, and Foreign Minister Mevlut Cavusoglu warned earlier this week that it would set back the already strained relationship between the two North Atlantic Treaty Organization allies.

“Statements that have no legal binding will have no benefit, but they will harm ties,” Mr. Cavusoglu said in an interview with the Turkish broadcaster Haberturk. “If the United States wants to worsen ties, the decision is theirs.”

The legal definition of genocide was not accepted until 1946, and officials and experts said Mr. Biden’s declaration would not carry any tangible penalties beyond humiliating Turkey and tainting its history with an inevitable comparison to the Holocaust.

“We stand firmly against attempts to pretend that this intentional, organized effort to destroy the Armenian people was anything other than a genocide,” a bipartisan group of 38 senators wrote in a letter to Mr. Biden last month, urging him to make the declaration. “You have correctly stated that American diplomacy and foreign policy must be rooted in our values, including respect for universal rights. Those values require us to acknowledge the truth and do what we can to prevent future genocides and other crimes against humanity.”

Mr. Biden appears intent on showing that his commitment to human rights — a pillar of his administration’s foreign policy — is worth any setback.

The genocide declaration signals that the United States is “willing to take geostrategic hits for our values,” said James F. Jeffrey, a former ambassador to Turkey who served in senior national security posts for the three presidents immediately preceding Mr. Biden.

Mr. Jeffrey, now the Middle East chair at the Wilson Center think tank in Washington, said there was little risk that Turkey would turn toward Russia, Iran or other American adversaries to replace its alliances with the West.

But, he said, Mr. Erdogan could easily try to stymie or delay specific policies to aggravate the Biden administration, particularly in Syria, where Turkey’s tenuous cease-fire with Russia has allowed for already-narrowing humanitarian access, and in the Black Sea, to which American warships must first pass through the Bosporus and the Dardanelles on support missions to Ukraine.

“It may be harder to get Erdogan to agree to specific policies,” Mr. Jeffrey said.

He also raised the prospect that Turkey could force meticulous reviews to slow non-NATO operations at Incirlik Air Base, a way station for American forces and equipment in the region. Or, Mr. Jeffrey said, Turkey could do something to provoke new sanctions or reimpose ones that have been suspended, like taking military action against Kurdish fighters allied with American forces against the Islamic State in northeast Syria.

Pentagon officials have also noted the value of Turkish forces remaining in Afghanistan after the withdrawal of U.S. and other coalition troops by Sept. 11; Kabul and Ankara have a longstanding relationship that will allow some troops to remain in Afghanistan after the NATO nations leave.

Tensions between Turkey and the United States flared in December, when the Trump administration imposed sanctions against Ankara for its purchase and then test of a Russian missile defense system that Western officials said could expose NATO’s security networks to Moscow. The sanctions were imposed in the final month of Mr. Trump’s presidency, three years after Turkey bought the missile system, and only after Congress required them as part of a military spending bill.

Mr. Trump had pointedly promised to help Armenia last fall during its war against Azerbaijan in the Nagorno-Karabakh region, noting the politically influential Armenian diaspora in the United States. His administration took a more evenhanded approach in trying to broker a peace agreement alongside Russia and France and, ultimately, Armenia surrendered the disputed territory in the conflict with Azerbaijan, which was backed by Turkey.

In the Wednesday interview, Mr. Aivazian, Armenia’s foreign minister, seized on Turkey’s military role in the Nagorno-Karabakh war as an example of what he described as “a source of expanding instability” in the region and the eastern Mediterranean Sea.

He said the genocide designation would serve as a reminder to the rest of the world if malign values are not countered.

“I believe bringing dangerous states to the international order will make our world much more secure,” Mr. Aivazian said. “And we will be witnessing less tragedies, less human losses, once the United States will reaffirm its moral leadership in these turbulent times.”