He describes Trump as a "demagogue"
Bernie Sanders has urged his supporters to vote for Hillary Clinton in order to block Donald Trump's path to the White House.
Speaking at a meeting just hours before the Democrats opened their convention in Philadelphia to nominate his primary rival, he described the Republican candidate a "demagogue" - (a political leader who seeks support by appealing to popular desires and prejudices rather than by using rational argument).
The Vermont senator said: "We have got to defeat Donald Trump. We have got to elect Hillary Clinton and her vice presidential running mate Tim Kaine".
Sanders and Clinton fought an at-times bitter primary campaign for the democratic nomination before Clinton emerged as the party's candidate to challenge Donald Trump.
Despite his calls, supporters cried out "we want Bernie" to which he responded: "Brothers and sisters, this is the real world that we live in," he said, adding, "Trump is a bully and a demagogue."
According to a CNN/ORC opinion poll, Trump has a three-point lead over Clinton, 48% to her 45%.
Clinton will formally accept the nomination on Thursday.