US President Joe Biden has formally announced that he is running for re-election in 2024, asking voters to give him more time to “finish the job” he began.

Mr Biden made his announcement in a video released by his new campaign team, in which he declares it is his job to defend American democracy.

It opens with imagery from the January 6, 2021, attack on the US Capitol by supporters of former president Donald Trump.

“When I ran for president four years ago, I said we’re in a battle for the soul of America, and we still are,” Mr Biden said.

“This is not a time to be complacent. That’s why I’m running for re-election.”

“Let’s finish this job. I know we can.”

Mr Biden described Republican platforms as threats to American freedom, vowing to fight efforts to limit women’s healthcare, cut social security and ban books, while blasting “MAGA extremists”.

MAGA is the acronym for the “Make America Great Again” political slogan of Mr Trump, who may well be Mr Biden’s Republican opponent in the November 2024 election.

In the two years since he took over from Mr Trump, Mr Biden won Congress’ approval for billions of dollars in federal funds to tackle the COVID-19 pandemic and for new infrastructure, and oversaw the lowest levels of unemployment since 1969, although a 40-year high in inflation has marred his economic record.

Mr Biden’s age, at 80, makes his re-election bid a historic and risky gamble for the Democratic Party, which faces a tough election map to hold the Senate in 2024, and is the minority in the House of Representatives now.

His approval ratings were stuck at just 39 per cent in a Reuters/Ipsos poll released on April 19 and there are concerns about his age among some Americans.

He would be 86 by the end of a prospective second term, almost a decade higher than the average US male’s life expectancy.

Doctors declared Mr Biden, who does not drink alcohol and exercises five times a week, “fit for duty” after an examination in February.

The White House says his record shows that he is mentally sharp enough for the rigours of the job.

Mr Biden will be joined in his 2024 quest by his running mate, Vice President Kamala Harris.

Reuters