Obama says Biden can 'heal' US in dark times as endorses ex-VP

Former US president Barack Obama formally endorsed Joe Biden's White House bid on Tuesday, saying his longtime deputy can unify and "heal" a nation struggling through some of its darkest moments.

"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.

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