Democratic Senator Kamala Harris says she will run for president in the 2020 election, the eighth name 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, adding 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 competes 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 or Indian American woman to be a major party nominee for the presidency.
At her first campaign event on Monday, at an African American university in Washington, she accused President Trump of holding Americans hostage by prolonging the partial government shutdown.
"[Pres. Trump] is now holding the American people hostage over a vanity project that he calls a wall, while 800,000 people are trying to figure out how they're going to pay their rent," Harris says."It is completely irresponsible." https://t.co/xyVGrbiFz4 pic.twitter.com/RHzkYjTDDg— CBS News (@CBSNews) January 21, 2019
Near the head of the pack
Kamala Harris is the kind of Democrat who could stick around and prevail in what is sure to be a gruelling nomination battle. She is from California, which is rich in both primary delegates and fundraising dollars. As a woman, and from an ethnic minority, she is well positioned to capitalise on her party's growing diversity.
She has one of the most liberal voting records in the US Senate at a time when Democrats are leaning to the left, but she also has a background as a hard-nosed prosecutor.
That background may end up a vulnerability as well, given that some progressives have criticised her for failing to support California criminal justice reform efforts and pointed to her prosecutorial record as being insufficiently sensitive to the rights of the accused. She will have to walk a fine line to tout her accomplishments while justifying her decisions.
Ms Harris has only been on the national stage two years, and not every political neophyte can hold up under fire the way Mr Obama did in 2008. She will be tested in the coming months, but she starts the contest near the head of the pack.
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 Oakland, California, on Sunday.
The senator deliberately picked Martin Luther King Jr Day, a national holiday, to make her announcement.
"The thing about Dr King that always inspires me is that he was aspirational," she said.
She added: "So today, the day we celebrate Dr King, is a very special day for all of us as Americans and I'm honoured to be able to make my announcement on the day we commemorate him."
Some observers also saw in her announcement another historical parallel.
The announcement was bathed in symbolism: Ms. Harris chose to enter the race on the Martin Luther King Jr. holiday, and her timing was also meant to evoke Shirley Chisholm, who was the first woman to seek the Democratic Party’s nomination for president https://t.co/GAKv1MqLWa— NYT National News (@NYTNational) January 21, 2019
Forty-seven years ago this week, Ms Chisholm, an African American New York congresswoman, became the first woman to run for the Democratic nomination.
Some noted that Ms Harris picked the same campaign colours, red and yellow, and both candidates professed to be the "candidate of the people".
The senator's staff told Buzzfeed her campaign logo was inspired by the Chisholm logo.