Kamala Harris declares 2020 presidential run

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.

Harris, who made history in 2016 as the first black woman elected to the U.S. Senate from California, timed her announcement for the U.S. Martin Luther King Jr. Day holiday honouring the slain civil rights leader. She said he was an aspirational leader.

The 54-year-old, a vocal critic of President Donald Trump, is described as a rising star within the party.

"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.

Harris, a former California state attorney general, has become popular with liberal activists for her tough questioning of Trump administration appointees and officials, including Supreme Court nominee Brett Kavanaugh and former Attorney General Jeff Sessions, during Senate hearings.

The 2020 Democratic presidential primary will be the first time more than one woman competes for the party's nomination.

Securing the nomination would make 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.

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.

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."