Hours before Republican candidates were to hold their final presidential debate of the year, one heavily focusing on security and immigration, Obama told 31 newly naturalized Americans that immigration is "who we are."
"Just about every nation in the world, to some extent, accepts immigrants, but there is something unique about America," he said in the National Archives rotunda, franked by the US Constitution, Bill of Rights and Declaration of Independence.
"We don't simply welcome new arrivals, we are born of immigrants, that is who we are, immigration is our origin story," he said.
"For more than two centuries its remained at the core of our national character, it's our oldest tradition, it's who we are, it's part of what makes us exceptional."
The campaign to succeed Obama has been marked by tough talk against immigrants and immigration, not least from Republican frontrunner Donald Trump.
The real estate mogul-turned-politician has vowed to ban all Muslims from entering the country and to deport illegal migrants from Latin America.
The debate has taken on a tougher tone amid terror attacks in Paris and California.
One of the husband and wife attackers who killed 14 people in San Bernardino was born in America, the other had arrived on a fiancee visa.
Listing instances of past discrimination against the Japanese, Irish and Italians, Obama said, "On days like today, we need to resolve to never repeat mistakes like that again."
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.