Democratic presidential candidate Joe Biden has selected Kamala Harris as his running mate in the upcoming US election.
She becomes the first black woman on a major presidential ticket in US history.
Sky News correspondent Sally Lockwood, who is in Washington DC, said: "This is indeed a historic moment and many said that Kamala Harris was the obvious frontrunner, she was the obvious candidate.
"It does indeed seem that Joe Biden agrees. We found out in the last few moments that the California senator will be running as his running mate in the election a little more than 80 days away.
"She is the first black female running mate for the two major parties, and only the third female running mate for the two major parties in American history."
In choosing Ms Harris, Mr Biden is embracing a former rival from the Democratic primary who is familiar with the pressures of a national campaign.
Ms Harris' presidential campaign collapsed months ago amid questions over her political identity.
Mr Biden had been pressed to select a woman of colour as his running mate as the US is in the midst of a reckoning over its history of racial injustice.
Ms Harris, who became the Senate's second Black woman in its history when she was elected in 2016, was always at the top of the list.
The 55-year-old first-term senator is one of the Democratic Party's most prominent figures
The California senator did anything but keep a low profile while Mr Biden was making up his mind over who to choose as a running mate.
She emerged as a fierce advocate for police reform and social justice as she sparred with Republicans on the Senate floor and offered fiery critiques of President Donald Trump.
Ms Harris joins Mr Biden in the 2020 race at a moment of unprecedented national crisis.
The coronavirus pandemic has claimed the lives of more than 150,000 people in the US, far more than the toll experienced in other countries.
Business closures and disruptions resulting from the pandemic have caused an economic collapse.
Unrest has emerged across the country as Americans protest racism and police brutality.
President Trump's uneven handling of the crises has given Mr Biden an opening, and he enters the autumn campaign in strong position against the president.
In adding Ms Harris to the ticket, he can point to her relatively centrist record on issues such as healthcare and her background in law enforcement in the nation's largest state.
Ms Harris' record as California attorney general and district attorney in San Francisco was heavily scrutinised during the Democratic primary.
She turned off some liberals and younger black voters who saw her as out of step on issues of systemic racism in the legal system and police brutality.
Mr Biden, who spent eight years as president Barack Obama's vice president, has spent months weighing who would fill that same role in his White House.
He pledged in March to select a woman as his vice president, easing frustration among Democrats that the presidential race would centre on two white men in their 70s.
A woman has never served as president or vice president in the United States.
Who is Kamala Harris?
Although a first-time senator, the 55-year-old quickly became a top contender for the number two spot after running her own White House campaign.
Ms Harris is a former California attorney general and has declared herself a "progressive prosecutor" who backs law enforcement reforms.
Born in Oakland to a Jamaican father and Indian mother, Ms Harris won her first election in 2003 when she became San Francisco's district attorney.
In that time, she created a re-entry programme for low-level drug offenders and cracked down on student truancy.
She was elected California's attorney general in 2010, making her the first woman and black person to hold the job.
In 2016, she was elected to the Senate and built a reputation around her work as a prosecutor.
Ms Harris gained attention for her forensic questioning of Trump administration officials and launched her presidential campaign early last year with the slogan "Kamala Harris For the People", referencing her work in the courtroom.