Joe Biden (L) and Senator Bernie Sanders greet each other with a safe elbow bump before the start of the 11th Democratic Party 2020 presidential debate in Washington. File / AFP
"I have concluded that this battle for the Democratic nomination will not be successful," the leftist Sanders told supporters in a livestream announcing he is dropping out.
"Vice president Biden will be the nominee," the 78-year-old added.
"I congratulate Joe Biden, a very decent man, who I will work with to move our progressive ideas forward."
Sanders, who challenged Hillary Clinton for the party's nomination in 2016, mounted a formidable challenge to Biden in the 2020 race, becoming the frontrunner early this year and earning the most votes in the first three state-wide contests.
But he was soon eclipsed by a surging Biden, who won the vast majority of the remaining primaries and now holds a commanding lead in the all-important race for delegates who choose the nominee.
Sanders ran an intense, issue-driven campaign, bringing his liberal ideological platform — including a call for universal health care and a $15 hourly minimum wage — into the mainstream.
"Together we have transformed American consciousness as to what kind of nation we can become, and have taken this country a major step forward in the never-ending struggle for economic justice, social justice, racial justice, and environmental justice," Sanders said.
Several US lawmakers have come out in support of such prescriptions, and Biden himself has shifted leftward to incorporate some Sanders policies, although he has stressed he does not support Sanders's Medicare for All plan.
Biden tweeted his thanks to Sanders, hailing him as "a good man, a great leader, and one of the most powerful voices for change in our country."
National youth poet laureate Amanda Gorman has become the youngest ever poet to read at a presidential inauguration after she read at the inauguration of Joe Biden. At age 22, the artist has made news before.
"OK, here we are again in the unusual position of not only interrupting the president of the United States but correcting the president of the United States,” said MSNBC anchor Brian Williams, as the network quickly ended its live coverage.
The Secret Service sent an extra squad of agents to Biden's campaign headquarters in Wilmington, Delaware as expectations rose that the Democratic candidate would be able to declare victory over President Donald Trump as early as Friday, the Post reported.
Minutes after major television networks declared Joe Biden the winner following four nail-biting days since the Nov.3 election, supporters banged pots, honked their car horns and set off fireworks across the US cities in exuberant celebration.
The latest precautionary measures must be observed, and performers and entertainers should be vaccinated against Covid-19.
On Monday the health ministry said around 280,000 cases and 4,106 deaths were confirmed in the last 24 hours. Both numbers are almost certainly undercounts.
Nearly 150,000 people were moved from their homes in the Indian state of Gujarat to safety on Monday and authorities closed ports and a main airport as the most intense cyclone in more than two decades roared up the west coast.