The emails of John Podesta, chair of Hillary Clinton's 2016 presidential campaign, were also compromised in a spear phishing attack, leading to the leak of 20,000 private emails.
Biden reached the threshold three days after the primaries because several states, overwhelmed by huge increases in mail ballots, took days to tabulate results.
The AP said Biden obtained the final votes he needed in primaries on Tuesday (June 2).
Prominent civil rights activist the Reverend Al Sharpton has told mourners George Floyd's fatal encounter with police and the nationwide protests against his death ignited have marked a reckoning for America over race and justice, demanding "Get your knee off our necks".
"Today, once again, I ask all Americans who feel downed, numbered and abandoned, to join our campaign", said Biden, increasingly keen.
Floyd's death has reignited long-felt anger over police killings of African-Americans and unleashed a nationwide wave of civil unrest unlike any seen in the United States since Martin Luther King Jr's 1968 assassination.
There's no place for violence, no place for looting or destroying property or burning churches or destroying businesses, many of them built by the very people of colour who were, the first time in their lives, were beginning to realise their dreams and build wealth for their families, he said. While 52 percent of registered voters supported Biden, Trump was backed by 41 percent voters. There are probably anywhere from 10-15pc of the people out there that are just not very good people. "There's never been anything we've been unable to do when we set our mind to do it, and we've done it together", he said. Asserting that the USA is a nation of values, Biden said that the freedom to speak is a cherished knowledge that lives inside every American nearly from the time one was a kid. "Leadership that can bring us together", the 77-year-old former senator from DE said.
Trump does lead Biden in some key battleground states. "I am used to people who in fact just try to exert power for their own egotistical reasons", he added. Such an approach, though, necessarily focuses on being more of an alternative to Trump than offering radically new political ideas.
"Together, we can win the battle for the soul of this nation", Biden wrote on Twitter as protests continued over the death of African-American George Floyd in white police hands and widespread outcries over racism.