The former US President Barack Obama has formally endorsed Joe Biden for the upcoming presidential election.

The 77-year-old served as Mr Obama’s vice president between 2009 and 2017.

In a 12-minute clip on social media, Mr Obama said choosing him as his vice president was “one of the best decisions I ever made” adding that he “became a close friend” during their time in the White House.

“I believe Joe has all the qualities we need in a president right now,” he said.

“Through all his trials, he's never once forgotten the values or moral fibre that his parents passed on to him, and made him who he is.”

I’m proud to endorse my friend @JoeBiden for President of the United States. Let's go: https://t.co/maHVGRozkX

— Barack Obama (@BarackObama) April 14, 2020

The move will give Mr Biden one of the biggest boosts of his campaign and help secure more support and funding in his bid to enter the Oval Office.

“Joe has the character and experience to guide us through one of our darkest times and heal us through a long recovery,” said Mr Obama.

In a thinly-veiled criticism of current President Donald Trump, Mr Obama said: “I know he will surround himself with good people.”

“Experts, scientists and military officials who actually know how to run the government and care about doing a good job running the government.

“Who know how to work with our allies and who will always put the American people’s interests above their own.”

Jill and Joe Biden at the 2020 Super Tuesday rally in Los Angeles, 09-04-2020. Image: Press Agency/SIPA USA/PA Images

He also slammed the Republican Party over its policies since returning to power.

“One thing everybody has learned by now is that the Republicans occupying the White House and running the US Senate are not interested in progress,” he said. “they are interested in power.”

“They have shown themselves willing to kick millions off their health insurance and eliminate pre-existing condition protections for million more.

“Even in the middle of this public health crisis. Even as they are willing to spend one trillion dollars on tax cuts for the wealthy.

“They have given polluters unlimited power to poison our air and our water and denied the science of climate change just as they denied the science of pandemics.”

Barack — This endorsement means the world to Jill and me. We’re going to build on the progress we made together, and there’s no one I’d rather have standing by my side. https://t.co/0mAjPZeYmd

— Joe Biden (@JoeBiden) April 14, 2020

On Twitter, Mr Biden said the endorsement “means the world to Jill and me.”

"We're going to build on the progress we made together, and there's no one I'd rather have standing by my side,” he said.

Mr Biden has leaned heavily on his connection with the former president throughout the campaign; however, up to now, Mr Obama has stayed silent on who will support.

Mr Biden became the Democratic Party’s sole remaining candidate for election after rival Bernie Sanders dropped out of the race last week.

Yesterday, Mr Sanders endorsed the 77-year-old for the White House.