Democratic Senator Kamala Harris says she will run for president in the 2020 election, the eighth person to join the battle for the party's nomination.
The California senator, who was elected in 2016, previously served as the state's attorney-general.
"I love my country," she told ABC's Good Morning America, saying she would "fight for the best of who we are".
The 54-year-old, a vocal critic of President Donald Trump, is described as a rising star within the party.
Elizabeth Warren, Kirsten Gillibrand, Tulsi Gabbard, John Delaney and Julian Castro are among those who have also announced their intentions to run.
"The future of our country depends on you and millions of others lifting our voices to fight for our American values. That's why I'm running for president of the United States," the senator said in a video posted on Twitter.
The 2020 Democratic presidential primary will be the first time more than one woman has competed for the party's nomination.
The race is already thought to be record-breaking, with four women candidates running national campaigns.
Securing the nomination would make Ms Harris the first African-American woman to be a major party nominee for the presidency.
"I have the unique experience of having been a leader in local government, state government and federal government," she said. "The American public wants a fighter ... and I'm prepared to do that."
Meanwhile, former Starbucks chief executive Howard Schultz is considering a run as an independent candidate, CNN reports.
Who is Kamala Harris?
She served two terms as district attorney of San Francisco (2004-2011), before being elected as attorney general of California (2011-2017), the first woman of colour to do so.
In 2017, the former prosecutor was sworn in as California's junior US senator.
She is the daughter of immigrants from Jamaica and India and has pushed back against critics of "identity politics".
"It is used to try and shut us up," Ms Harris told a conference last summer.
Her tough questioning of Justice Brett Kavanaugh about his views on abortion and the ongoing investigation into alleged Russian interference in the 2016 election attracted attention from Democrats.
But she has also faced criticism for saying she was not aware of allegations of sexual harassment against one of her aides, who resigned in 2016.
Ms Harris plans to launch her campaign during a rally in California on Sunday.