WASHINGTON -- U.S. Vice President Kamala Harris vowed to keep fighting for the ideals that powered her presidential campaign on Wednesday in a concession speech that acknowledged President-elect Donald Trump's win while warning of potential dark times to come.

"While I concede this election, I do not concede the fight that fueled this campaign," she told supporters, many of them in tears, at her alma mater Howard University, a historically Black college in Washington.

Harris, her voice at times wavering, pledged to continue fighting for women's rights and against gun violence and to "fight for the dignity that all people deserve."

She said she had called Trump, congratulated him on his triumph in Tuesday's presidential election and promised to engage in a peaceful transfer of power.

"The outcome of this election is not what we wanted, not what we fought for, not what we voted for, but hear me when I say - hear me when I say: The light of America's promise will always burn bright," she said.

The somber mood was in striking contrast to the homecoming celebration a few weeks ago on the Howard campus when thousands of students and alumni gathered ahead of what they hoped would be the election of the country's first graduate of historically Black Colleges and Universities as president.

Harris addressed a crowd on Wednesday that included former House Speaker Nancy Pelosi, aides in President Joe Biden's White House and thousands of fans. Harris' campaign anthem, Beyonce's "Freedom," played as she entered the stage.

Her running mate, Minnesota Governor Tim Walz, joined the crowd.

"A fundamental principle of American democracy is that when we lose an election, we accept the results. That principle, as much as any other, distinguishes democracy from monarchy or tyranny, and anyone who seeks the public trust must honor it," Harris said, in a nod at Trump's efforts, before he won, to sow doubt about the legitimacy of the election.

Trump claims falsely that he won the 2020 election, which he lost to Biden.

Harris encouraged her supporters, especially young people, not to give up even in their disappointment and said: "Sometimes the fight takes a while. That doesn't mean we won't win."

Harris rose to the top of the Democratic ticket in July after Biden stepped aside. She brought new-found enthusiasm and cash to the effort, but she struggled to overcome voters' concerns about the economy and immigration.

"I know many people feel like we are entering a dark time, but for the benefit of us all, I hope that is not the case. But here's the thing: America, if it is, let us fill the sky with the light of a brilliant, brilliant billion of stars ... the light of optimism, of faith, of truth and service," she said.

Thousands had gathered at the school on Tuesday night for what they hoped would be a historic victory for the first woman to become president. They came back on Wednesday to show their support and rue her loss.

Jamela Joseph, 31, a doctoral student at Howard, said: "America had its opportunity to move forward in a progressive and intentional manner, and as a nation it has, you know, shown that it's going to repeat itself and its history and its legacy of upholding white supremacy racism, in terms of treating women as second class citizens."

Donna Bruce, 72, said she had come to show love and respect for what Harris had done. She noted she had just seen a little girl with a T-shirt that said: "A Black girl will save the world."

"I still believe that," Bruce said. "It may not be this Black girl, but I believe a Black girl will."