The announcement of his run for the 2024 election comes four years to the day since he declared his initial bid for the White House by promising to heal the "soul of the nation" amid the turbulent administration of former president Donald Trump.

Already the oldest president in history - Mr Biden would be 86 at the end of a second term.

Mr Biden said in a pre-recorded video message: "Personal freedom is fundamental to who we are as Americans. There's nothing more important. Nothing more sacred.

"That's been the work of my first term: To fight for our democracy.

'MAGA extremists are lining up to take those bedrock freedoms away'

"This shouldn't be a red or blue issue. To protect our rights. To make sure that everyone in this country is treated equally. And that everyone is given a fair shot at making it.

"But around the country, MAGA extremists are lining up to take those bedrock freedoms away. Cutting social security that you've paid for your entire life while cutting taxes for the very wealthy.

"Dictating what health care decisions women can make, banning books, and telling people who they can love. All while making it more difficult for you to be able to vote.

"When I ran for president four years ago, I said we are in a battle for the soul of America. And we still are.

"The question we are facing is whether in the years ahead we have more freedom or less freedom. More rights or fewer.

"I know what I want the answer to be and I think you do too. This is not a time to be complacent. That's why I'm running for re-election."

In a statement on Twitter, Ms Harris said: "As Americans, we believe in freedom and liberty-and we believe that our democracy will only be as strong as our willingness to fight for it. That's why @JoeBiden and I are running for reelection."

A notable swath of Democratic voters have indicated they would prefer he not run, in part because of his age - concerns Mr Biden himself has called "totally legitimate".

A recent poll from The Associated Press-NORC Centre for Public Affairs Research showed just 47% of Democrats said they wanted him to seek a second term, up from 37% in February.

It comes a day after he told Sky News of his intention to go for re-election.

Read more US News:
Jury selection to start in Donald Trump's civil rape trial
Jackass star Bam Margera wanted by police

Mr Trump officially launched his third bid for the US presidency in November 2022.

The 76-year-old can still run for office despite being the first current or former US president to be charged with a crime.

He has pleaded not guilty to 34 felony counts of falsifying business records and conspiracy for his alleged role in hush money payments to two women towards the end of his 2016 presidential campaign.