He has said that he will step aside as a candidate and he will focus on fulfilling his duties as President for the remainder of his term.

He adds he's going to speak to the nation later about his decision.

So this information has come to us via ex-formerly known as Twitter, the social media platform, where Joe Biden has posted a letter.

It reads, my fellow Americans, over the past three and a half years, we've made great progress as a nation.

Today, America has the strongest economy in the world.

We have made historic investments in rebuilding our nation, in lowering prescription drug costs for seniors and in expanding affordable health care to a record number of Americans.

We've provided critically needed care to a million veterans exposed to toxic substances, passed the first gun safety law in 30 years, appointed the first African-American woman to the Supreme Court and passed the most significant climate legislation in the history of the world.

America has never been better positioned to lead than we are today.

I know none of this could have been done without you, the American people.

Together, we overcame a once-in-a-century pandemic and the worst economic crisis since the Great Depression.

We've protected and preserved our democracy and we've revitalized and strengthened our alliances around the world.

It's been the greatest honor of my life to serve as your president.

And while it has been my intention to seek re-election, I believe it is in the best interests of my party and the country for me to stand down and to focus solely on fulfilling my duties as president for the remainder of my term.

I will speak to the nation later this week in more detail about my decision.

For now, let me express my deepest gratitude to all of those who have worked so hard to see me re-elected.

I want to thank Vice President Kamala Harris for being an extraordinary partner in all this work.

And let me express my heartfelt appreciation to the American people for the faith and trust you've placed in me.

I believe today what I always have, that there is nothing America can't do when we do it together.

We just have to remember we are the United States of America.

So that is the letter that has been posted in the last 10 minutes on X, formerly known as Twitter social media platform.

And it was only 18 hours ago that on that same social media account, Joe Biden said that this is the most important election of our lifetimes and I will win it.

But of course, we've seen over the last few weeks, growing amounts of We know that he's been isolating because he was found to have COVID, but we were expecting him to return to the campaign trail tomorrow, having been told by his doctor that his health was improving and that he was fit to continue campaigning.

But a growing number of Democrats, including senior Democrats, have expressed concern that he is not fit enough to continue in the campaign.

Let's speak to our correspondent, David Waddell, who's following this live and developing story.

So David, we found out about it, as is the way in 2024 on social media.

Yes, indeed, not just a tweet in this case, but a whole letter.

And I've just been reading through it.

You've read some of it on air in recent minutes out in the newsroom.

We're dashing to cover this as best as we can for you.

Let me just bring you some of the details of the letter.

The President Joe Biden said today, America has the strongest economy in the world.

He's gone on to detail some of the achievements of his presidency, but then goes on to say that he believes it's in the best interest of his party in the country for him to stand down and to focus solely on fulfilling his duties as president for the remainder of his term, which is what, six or seven months or so, and allow a successor to take on the mantle of challenging the presidency as the Democratic candidate in November.

The pressure was growing on him, though, wasn't it?

Some donors were concerned about whether he was fit to stand.

And as we've seen, several senators have also come forward to say it's now time to go.

So one had to wonder when the pressure would become so great that he needed to listen to what his party was saying.

Well, yes, indeed.

And there are a couple of different issues here, one borne, perhaps, of the other.

There have been a few missteps in terms of his ability to appear like he had a handle on his brief, and that then led to question marks over whether he had the capacity to continue as president or, indeed, whether he had the capacity to continue as next year.

And with growing doubts over that, both amongst those people close to him and also amongst the wider American public, there were questions over whether he should continue to fight for the presidency in November.

That then has spilled over to a further issue, which is the polling figures.

And those have suggested for some time now that his rival, Donald Trump, the previous president, would be likely to win.

And that has put further pressure on President Biden.