United States President Joe Biden has officially launched his campaign for re-election in 2024, becoming the Democratic frontrunner in a race that could pit him for a second time against Republican contender Donald Trump.

Biden’s announcement in a video on Tuesday came on the fourth anniversary of the start of his first successful presidential bid.

A majority of Democrats would back Biden, 80, against a Republican challenger in next year’s election, a recent poll found.

But the Democratic president faces some of the lowest approval ratings of his tenure so far, and his age – Biden is currently the oldest person to ever hold the highest US office – has spurred questions about his re-election prospects.

“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”, - Biden said in his campaign video.