Sanders, who dropped out of the Democratic primary competition last week leaving Biden as the last standing candidate, joined the former vice president on a livestream over social media to issue the endorsement.

Sanders called on people to "come together" to back Biden.

"We need you in the White House," he said to Biden, adding that it was an imperative for the party to prevent Trump from getting a second term.

Sanders, a senator from Vermont, ran on a ticket that pushed an expansive government takeover of health care that would have provided coverage to all people in the United States, on top of other progressive ideas that were at times dubbed revolutionary.

Biden is a long-time member of the party establishment having served as a senator for decades, and was vice president under former president Barack Obama.

Australian Associated Press