US Senator Elizabeth Warren has endorsed former Vice President Joe Biden for president, delivering another high-profile backing from one of his former rivals as he aims to unify the Democratic Party ahead of a bruising contest with Republican President Donald Trump.
"In this moment of crisis, it's more important than ever that the next president restores Americans' faith in good, effective government — and I've seen Joe Biden help our nation rebuild," Ms Warren wrote in a tweet.
"Today, I'm proud to endorse Joe Biden as President of the United States."
Ms Warren, a liberal who ended her own bid for the White House last month, gave Mr Biden his third major endorsement of the week.
Former US President Barack Obama backed Mr Biden yesterday.
In recent weeks, the more moderate Mr Biden has made overtures to liberal backers of Mr Sanders and Ms Warren.
After Mr Sanders' departure from the race, Mr Biden's campaign shifted left on two of his top priorities, student debt and Medicare, and the two men said during a joint video appearance on Monday that they would create working groups to address major policy areas.
Mr Biden also adopted Ms Warren's sweeping plan on bankruptcy, a striking move given that the two rivals had clashed for more than a decade over legislation that Mr Biden backed making it harder to file for bankruptcy protection.
Mr Biden and Ms Warren have had "several calls" since she ended her campaign, a source familiar with the discussions told Reuters.
In a video announcing her endorsement, Ms Warren noted she didn't agree with Mr Biden all the time but praised his willingness to adapt.
"One thing I appreciate about Joe Biden is he will always tell you where he stands," she said.
"When you disagree - he'll listen. ... And he's shown throughout this campaign that when you come up with new facts or a good argument, he's not too afraid - or too proud - to be persuaded."
