Biden picks Kamala Harris as running mate

US Democratic presidential candidate Joe Biden has picked Senator Kamala Harris of California as his running mate, making her the first black woman and the first Asian American on a major presidential ticket.

"I have the great honor to announce that I've picked@KamalaHarris－a fearless fighter for the little guy, and one of the country's finest public servants－as my running mate," Biden wrote on Tuesday on Twitter.

The daughter of an Indian mother and a Jamaican father, Harris has knocked down barriers throughout her career. She became the first woman elected to serve as San Francisco's district attorney in 2003, and, in 2010, the first woman elected to serve as California's attorney general.

"Now Joe has an ideal partner to help him tackle the very real challenges America faces right now and in the years ahead," said former United States president Barack Obama, for whom Biden served as vice-president.

US President Donald Trump said on Tuesday that Biden had "roped himself" into picking a female running mate, adding that "some people would say that men are insulted by that. And some people would say it's fine. I don't know".

Biden vowed to choose a woman as his running mate in March. In the wake of protests following the May 25 death of George Floyd over racial injustice and police brutality against African Americans, Biden had been under pressure to pick a woman of color as his running mate.

Harris, 55, who became only the second black woman to serve in the Senate when she was elected in 2016, can be expected to help Democrats' efforts to secure votes from African Americans, one of the party's most loyal constituencies.

Harris said she was "honored" to join the ticket and would "do what it takes" to help Biden win.

She said on social media that Biden "can unify the American people because he's spent his life fighting for us. And as president, he'll build an America that lives up to our ideals".

The Trump campaign released a video over Twitter on Tuesday in which a narrator says: "Voters rejected Harris. They smartly spotted a phony. But not Joe Biden. He's not that smart.… He is handing over the reins to Kamala while they hand over the reins to the radical left."

But Trump donated $6,000 total in 2011 and 2013 to Harris when she was running for reelection as California's attorney general.

Harris abandoned her own presidential run in December and endorsed Biden on March 8. Harris will now be relied on to be a battle-tested partner for going on the offensive against Trump and Vice-President Mike Pence. Harris is scheduled to debate Pence on Oct 7 in Salt Lake City, Utah.

Biden, who turns 78 on Nov 20, would be the oldest person to become US president if elected. His age has led to speculation he may serve only one term, making Harris a potential top contender in 2024.

Reuters contributed to this story.