WASHINGTON (REUTERS) - United States Senator Elizabeth Warren endorsed former vice-president Joe Biden for president on Wednesday (April 15), giving the presumptive Democratic front runner another high-profile backing from one of his former rivals.

"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, gives Mr Biden his third major endorsement of the week, as he looks ahead to November's contest with Republican President Donald Trump.

Mr Biden's chief rival, Senator Bernie Sanders, endorsed him on Monday after suspending his campaign last week, while former president Barack Obama backed Mr Biden on Tuesday.

Like Mr Sanders' endorsement, Ms Warren's support for Mr Biden could help him make inroads with the party's left wing.