Vice President Kamala Harris on Monday made her first public appearance since President Joe Biden dropped out of the 2024 race and endorsed her.

Harris gave remarks at an event celebrating the NCAA championship teams Monday morning on the South Lawn of the White House. She was filling in for Biden, who is recovering from COVID.

"I wanted to say a few words about our president. Joe Biden's legacy of accomplishment over the past three years is unmatched in modern history," Harris said. "In one term, he has already surpassed the legacy of most presidents who have served two terms in office."

Harris didn't specifically address her own candidacy, but said she was grateful for Biden's service to the country.

"I am first-hand witness that every day our president, Joe Biden, fights for American people. And we are deeply, deeply grateful for his service to our nation," she said.

The comments came just a day after Biden announced he was ending his campaign. He said in a statement on Sunday that he will "stand down," a move he said was "is in the best interest of my party and the country."

Biden said he will speak about his decision when he addresses the nation later this week.

In a separate post on X, Biden gave his "full support and endorsement" for Harris to be the Democratic Party's nominee. Since then, many others in the Democratic Party have announced they will back her -- including some considered to be contenders for the presidency in the case that Biden dropped out, such as Govs. Gretchen Whitmer of Michigan, JB Pritzker of Illinois and Gavin Newsom of California.

"I first came to know President Biden through his son Beau. We worked together as attorneys general in our states," Harris said at the White House event, referring to his late son.

"And back then, Beau would often tell me stories about his dad. He would talk about the kind of father and the kind of man that Joe Biden is. The qualities that Beau revered in his father are the same qualities that I have seen every day in our president. His honesty, his integrity, his commitment to his faith and his family, his big heart and his love, deep love of our country," she said.

Following her remarks about Biden, Harris turned back to honoring the attendees, the NCAA champions from the past college year. She transitioned into a speech about sports and the journey the athletes in the audience have taken to get to their point of victory.

"Here today, we have seven undefeated teams, 11 repeat champions and 20 first time winners," Harris said. "Some of you have represented our nation on the international stage in world cups and world championships. And later this month, six of you will represent our nation at the 2024 Olympics in Paris."

ABC News' Molly Nagle, Mary Bruce, Michelle Stoddart and Cheyenne Haslett contributed to this report.