Barack Obama will endorse his longtime deputy Joe Biden for US president Tuesday, sources close to the former commander in chief said, as the Democratic Party rallies around its flagbearer ahead of November's election. Obama, a popular two-term president and Donald Trump's predecessor in the White House, will release a video Tuesday with his endorsement of Biden, the sources said. The 77-year-old former vice president is the Democratic Party's presumptive nominee, after his lone remaining rival Bernie Sanders dropped out of the race last week and endorsed Biden on Monday. jca-mlm/jm