Former President Obama endorses Biden's 2020 presidential campaign

Former US President Barack Obama on Tuesdayendorsed Joe Biden's presidential campaign, saying his longtime vice president can unify and "heal" a nation struggling through some of its darkest moments.

The formal backing by perhaps the most popular politician in America is the latest shot in the arm for Biden's surging candidacy, and a further sign that Democratic leaders are rallying around the party flagbearer ahead of November's election.

"Joe has the character and the experience to guide us through one of our darkest times and heal us through a long recovery," Obama said in a 12-minute video filmed at his home in Washington and released online.

"I believe Joe has all the qualities we need in a President right now," Obama said, calling his choice of Biden as running mate in 2008 "one of the best decisions I ever made."

The 77-year-old former vice president and Democratic stalwart is the party's presumptive nominee to challenge Donald Trump, after his lone remaining rival Bernie Sanders dropped out of the race last week.

(With inputs from AFP)