Sen. Bernie Sanders on Monday endorsed his longtime rival former Vice President Joe Biden, a move aimed at unifying a Democratic Party long fractured along moderate and liberal lines ahead of the election match-up against President Donald Trump.

Sanders cited the novel coronavirus outbreak as a reason for the party to come together behind Biden, the likely Democratic presidential nominee after the progressive firebrand Sanders suspended his White House campaign.

Sanders' endorsement during an online campaign event came as Biden's team had already begun reaching out to advocacy groups on the left to enlist their support for the Nov. 3 general election battle against the Republican Trump.