WASHINGTON — US Senator Bernie Sanders endorsed his former 2020 presidential primary rival and the presumptive Democratic Party presidential nominee Joe Biden on Monday in a surprise joint livestream with the two men. Sanders had pulled out of the contest last week, leaving Biden as the only remaining candidate. The Vermont senator, 78, urged all Americans to unite to defeat Trump, describing the US president as "the most dangerous president in the modern history of this country". "Today I am asking all Americans — I"m asking every Democrat, I"m asking every independent, I"m asking a lot of Republicans — to come together in this campaign to support your candidacy which I endorse," Sanders said. "It"s imperative that all of us work together." Sanders’ support of the former vice president comes at a critical moment in the 2020 campaign, as Biden attempts to unify the party after a fiercely contested primary. By throwing his weight behind Biden, Sanders, is sending a clear signal to his legions of loyal followers that they should align behind the party’s nominee to defeat Trump. Thanking his former rival and the leftist leader, Biden, 77, said he was "deeply grateful" for the endorsement and said he needed Sanders not just for the campaign, but to govern. "You"ve put the interests of this nation and the need to beat Donald Trump above all else. As you say — "Not me, us"," he said. Addressing Sander"s supporters, Biden added: "I see you, I hear you, I understand the urgency of what it is that we have to get done in this country, and I hope you"ll join us." Biden still faces deep skepticism from young progressive voters, many of whom supported Sanders by lopsided margins. — Agencies