Former US vice-president Joe Biden has formally joined the Democratic presidential contest.
After more than three decades as a senator, Biden's profile rose significantly after he became Barack Obama's second-in-command.
Having been widely expected to join the race, the 76-year-old officially announced his bid through a video posted this morning:
The core values of this nation… our standing in the world… our very democracy...everything that has made America -- America --is at stake. That’s why today I’m announcing my candidacy for President of the United States. #Joe2020 https://t.co/jzaQbyTEz3
— Joe Biden (@JoeBiden) April 25, 2019
He previously ran two unsuccessful campaigns to secure the Democratic presidential nomination - in 1988 and 2008.
The field now features at least 20 Democrats looking for the chance to take on President Donald Trump next year.
Biden is seen as a front-runner, although a number of recent polls have shown a tight race between the former vice-president and independent Senator Bernie Sanders.
Other Democratic candidates include a half dozen senators, such as Elizabeth Warren and Kamala Harris.
Younger hopefuls such as Texas politician Beto O'Rourke and Pete Buttigieg - the mayor of South Bend, Indiana - have also featured prominently in recent opinion polls.