Democratic presidential candidate Joe Biden has named Kamala Harris as his running mate – the first black woman and South Asian American in the role.
The former California attorney general has been urging police reform amid nationwide anti-racism protests.
Mr. Biden will face President Donald Trump in the election on 3 November.
After Tuesday’s announcement, Ms. Harris tweeted that Mr. 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.
“I’m honored to join him as our party’s nominee for Vice President, and do what it takes to make him our Commander-in-Chief.”
Mr. Biden and Ms. Harris will deliver remarks in Wilmington, Delaware, on Wednesday afternoon on “working together to restore the soul of the nation and fight for working families to move the country forward”, the Biden campaign said.
At a White House news conference on Tuesday, Mr. Trump, a Republican, said he was pleased with Mr. Biden’s choice, adding that Ms. Harris did “very, very poorly” in her effort to become the Democratic nominee.
Ms. Harris will take part in a debate with Mr. Trump’s running mate, Vice-President Mike Pence, on 7 October in Salt Lake City, Utah.
In last year’s race to be the Democratic nominee, Kamala Harris showed herself to be a forceful speaker, launching blistering attacks on Donald Trump.
Biden VP pick: Kamala Harris chosen as running mate
Ms. Harris, 55, dropped out of the presidential race in December after failing to make headway in her bid to win the Democratic nomination.
She repeatedly clashed with Mr. Biden during the primary election debates, most notably criticizing his praise for the “civil” working relationship he had with former senators who favored racial segregation.
Ms. Harris was born in Oakland, California, to two immigrant parents: an Indian-born mother and Jamaican-born father.