Senator Bernie Sanders has quit the presidential race, clearing the way for Joe Biden to take on Donald Trump in the November election.
The two politicians, who had spent the last year battling for the Democratic nomination, appeared to put on a united front on Monday.
They appeared together by split-screen on Biden's livecast, where he appealed to all Americans to unite to defeat Trump.
Sanders urged the voters "to come together in this campaign to support (Biden's) candidacy, which I endorse, to make certain that we defeat somebody who I believe ... is the most dangerous president in the modern history of this country."
He put up a united front, telling voters that "it's imperative that all of us work together."
Before the Democratic primary contest was halted due to the pandemic, Biden had secured a commanding edge over Sanders.
The US military said on Saturday it carried out multiple strikes in Syria targeting ISIS as part of an operation that Washington launched in December after an attack on American personnel.
Israeli fire killed at least three Palestinians in two separate incidents across Gaza, local health authorities said, as tension rises over continued violence.
Tens of thousands of people marched through Minneapolis on Saturday to decry the fatal shooting of a woman by a US immigration agent, part of more than 1,000 rallies planned nationwide over the weekend against the federal government's deportation drive.
At least one person has died in Australia's southeast where bushfires raging for days have razed buildings, cut power to thousands of homes and burned swathes of bushland, police said on Sunday.