Speaking at a campaign rally, former President Donald Trump says that Democrats are having a "full-scale breakdown" and challenged US President Joe Biden to another debate without moderators
Biden and his campaign have faced growing pressure to step aside after a widely-panned debate performance against Trump last month
Biden was in Washington DC today, and emphasised the importance of Nato at the opening of the alliance's summit
During the speech, he Ukraine would receive "dozens of additional tactical air defence systems"
With his re-election campaign facing intense scrutiny, Biden appeared to use the speech to contrast his foreign policy views with Trump's
Earlier in the day, the White House news briefing grew heated when reporters pressed for more information about Biden's health and fitness
Democratic lawmakers have held meetings today after concerns were raised about Biden's ability to beat Trump in the race for the White House
Joe Biden, speaking in a clear, firm voice, beings to speak.
He invokes the history of Nato, remarking that his speech was being held in the same venue where the original treaty was signed 75 years ago.
"Today, Nato is more powerful than ever, 32 nations strong," he said.
Image source, PoolPresident Joe Biden has now taken to the podium - we'll bring you his remarks as they're made.
Several singers, clad in military best, are now singing a rendition of Rodgers and Hammerstein's You'll Never Walk Alone, the anthem of Liverpool FC, which has also been famously sung by Elvis.
It goes a little something like this:
Walk on, walk onWith hope in your heart.And you'll never walk aloneYou'll neverEver walk alone
"I do not know what the next crisis will be but I do know what we are at our best when we take difficult decisions with political courage and moral clarity," says Stoltenberg.
"And I do know that we are stronger and safer with Nato. It is good to have friends."
With that he concludes his remarks.
Stoltenberg calls Russia's war against Ukraine the "biggest security crisis in generations".
"The biggest cost" and greatest risk would be "if Russia wins in Ukraine", he said. "We cannot let that happen."
He added that countries such as North Korea wanted Russia to win, and Nato to fail.
"The time to stand for freedom and democracy is now. The place is Ukraine," he said.
Nato Secretary General Jens Stoltenberg beings his remarks by noting that the Nato alliance was first formed by leaders 75 years ago in the same auditorium where he is speaking today.
He said the leaders formed the group "with a clear purpose to preserve peace and safeguard freedom".
Speaking of the Nato charter, he says: "Never has so few words meant so much to so many."
He goes on to call it "the most successful alliance in history", enduring longer than any other.
Image source, Getty ImagesThere is a great deal of history behind this summit, which marks the alliance's 75th anniversary.
Archive video is played before Biden's speech, with footage from World War Two and its aftermath, and key moments from Nato's history.
"That alliance becomes an identity, an expression of who we are as people," a voiceover says as footage shows former world leaders shaking hands. "Those partnerships make us all stronger."
The leaders of the Nato countries have now taken the stage in Washington, and are standing shoulder-to-shoulder.
The highly scripted event coincides with swelling classical music.
Image source, Getty ImagesUS President Joe Biden and other Nato leaders are walking onto the stage in Washington DC, where he is opening the Nato 75th anniversary summit.
Stick with us as we bring you the news and analysis from Biden's speech and beyond.
You can watch his speech by clicking the 'watch live' button above.
Anthony Zurcher
BBC North America correspondent
Joe Biden continues his walk across a political high wire tonight, with his speech to gathered leaders at the Nato summit. He’ll have an audience both in the US and across the world that will be watching for any sign of stumble or verbal miscue.
It’s the kind of occasion to which the president has risen even in the recent past – a set piece event, delivered via teleprompter in a controlled environment. His State of the Union address in March, which also came amidst doubts about his age and abilities, was delivered with vigour. Even his rally speech the day after his ill-fated debate performance was full of energy.
The real test for Biden this week will be at his press conference on Thursday afternoon, not his speech tonight, important though it may be. There, the president will have to think on his feet and respond in an unscripted situation under pressure.
An uneven performance there could rekindle the worst fears of already anxious Democrats
Predecessor Donald Trump has taken to social media to claim credit for an increase in defence spending by Nato countries.
"If it weren’t for me as president, there probably would be no Nato by now," he claimed on Truth Social.
He said that after learning that several Nato countries were not "paid up... I found this unacceptable, and insisted that they pay if they wanted the protection of the US".
"Billions of dollars came pouring in."
The Nato doctrine requires member states to spend at least 2% of their GDP on the military.
Nato countries have contributed significantly more to defence spending in the last two years, while Biden has been president and as the war in Ukraine rages.
But many have still yet to hit the 2% target.
Courtney Subramanian
Assistant editor, BBC News, Washington
Vice-President Kamala Harris arrived in Las Vegas on Tuesday, as President Biden prepared to kick off the Nato summit.
The summit is geared to highlight his stewardship of the trans-Atlantic alliance - but instead would serve as the latest test of whether he's fit for office.
Harris, who has been discussed as the most-likely replacement for Biden should he decide to step down, has been unequivocal in her support for her running mate. And the president has defiantly declared he has no plans of dropping out.
In the wake of his disastrous debate, Harris has continued to hit the campaign trail. She has focused on prosecuting the case against Donald Trump and refused to address questions about her - and Biden's - political future.
The vice-president will speak at a campaign event for Asian American, Native Hawaiian and Pacific Islander communities in Nevada. It is her sixth visit to the battleground state this year.
On Wednesday, she will deliver a speech at the annual convention for Alpha Kappa Alpha, a historically black international service organisation and sorority.
As leaders begin to arrive to the historic Mellon Auditorium, the band inside the room where President Joe Biden is due to speak has started rehearsing. The sounds of trombones, violins, and drums is adding to the anticipation building in the auditorium ahead of his remarks tonight.
Here's a look at a few of the Nato leader we've seen filing in, where Biden is set to speak in just a few minutes.
You can watch Biden's speech right here by clicking the "Watch live" button above.
Image source, Getty ImagesDenmark's Prime Minister Mette Frederiksen and her husband Bo Tengberg
Image source, Getty ImagesOlaf Scholz, Chancellor of Germany, and his wife Britta Ernst
Image source, Getty ImagesCanadian Prime Minister Justin Trudeau
Image source, Getty ImagesItalian Prime Minister Giorgia Meloni
Image source, Getty ImagesUS Treasury Secretary Janet Yellen has told Congress that Biden is actively engaged during important meetings that she has attended.
"The president is extremely effective in the meetings that I've been in with him," Yellen told the House Financial Services Committee on Tuesday, according to Reuters.
"That includes many international meetings that are multi-hour, like his meetings with President Xi" of China, she said.
She declined to respond to questions from the Republican-controlled committee about when she last spoke to Biden.
Asked if she and other cabinet members had met to discuss removing him by invoking the 25th Amendment of the US Constitution, she said "no".
The amendment allows the president's top aides to force him out of office and transfer the job to the vice-president.
Kayla Epstein
Senior journalist
A new poll, external by a Democratic firm found that Vice President Kamala Harris slightly leads Donald Trump in a hypothetical matchup for president between the two politicians, POLITICO reported.
Right now, the poll is purely speculative, as Joe Biden has vowed to stay in the race.
The poll of 1000 registered voters, conducted by a firm called Bendixen & Amandi, indicates Harris could lead Trump 42% to 41%, with 12% of voters undecided.
Biden himself, meanwhile, trailed Trump by a single percentage point.
The pollsters also asked about a hypothetical matchup between Trump and his 2016, opponent, Hillary Clinton, and found she led 43% to 41%.
Biden is by no means out of the race, as he and Trump have jockeyed closely in the polls for months. America's highly partisan environment means that only a sliver of voters are truly up for grabs.
But polls this week have shown Biden took a hit from his disastrous debate performance. A New York Times poll , externalfound Trump leading him 49% to 43%, the largest lead the Times has ever measured for Trump since 2015.
Helena Humphrey
reporting from Washington
As we wait for Biden to take the stage at the Mellon Auditorium, I’m leafing through the evening's programme left on every seat.
Inside, there's a message from the US president that offers a sneak peek at his likely talking points.
One line stands out: "Today, Nato is stronger than it has ever been: 32 nations strong." Under the Biden administration, both Sweden and Finland have joined, and defence spending is up.
And then there’s this, the founding Nato principle: “We recognize that we are stronger when we are united and that threats to one are threats to all.”
This is a stark contrast to former President Donald Trump’s February remark, suggesting he would “encourage” Russia to “do whatever the hell they want” to Nato allies who don’t pay enough.
Those are just a few clues to what we can expect in the Biden's address, as some allies fret over what a second Trump presidency could mean for the future of the alliance.
Rachel Looker
Reporting from Capitol Hill
Chris Coons, a Democrat senator from Delaware who co-chairs Biden’s re-election campaign, said there should be as much focus on the president's opponent than the debate performance.
"Every day that we are talking about this issue... we're not talking about the real threat to American security posed by Donald Trump, especially during Nato week,” he said.
"We should be focusing on that at least as much as concerns about whether Joe Biden does a press conference,” he added.
Coons called Biden “the most consequential presidential” of his lifetime, adding that he has always had a stutter and has occasionally misspoke.
"His record speaks for itself and I think that's why you're seeing more and more Democrats speak out strongly in support of him,” Coons said.
Rachel Looker
Reporting from Capitol Hill
Democrat and independent politicians have continued to air their opinions on Joe Biden's re-election bid after his disastrous debate performance.
Senator Joe Manchin, an independent from West Virginia, called this week on Capitol Hill “crucial” for resolving concerns.
"This is the first week we’ve come back since everything has happened where everybody's talking to every body," he said.
Pennsylvania senator John Fetterman said he didn't understand why people were fixated on Biden's debate performance compared to Donald Trump's record.
“Maybe we can encourage Joe Biden to bang a porn star or maybe he could become consumed with revenge and now say crazy things and now have a plan for 2025 to make him more popular,” Fetterman said, referencing Trump's criminal record for falsifying business records and his policy proposals.
Connecticut senator Richard Blumenthal re-iterated his support for Biden.
"He needs to make his case aggressively and vigorously to the American people, but I sense increasing strength among my colleagues and the public.
“The one point that I think is ignored is the guts and the grit it takes to get through what Joe Biden is doing right now.
Helena Humphrey
reporting from Washington
It's a busy (and hot) day here in Washington DC.
Our reporting team has arrived at the Mellon Auditorium for the first night of the Nato summit.
Anticipation is building here ahead of President Joe Biden’s speech here this evening. And the stakes couldn’t be higher.
This place is historic - it’s where the founding Nato treaty was signed back in 1949. Tonight, Democrats are hoping it doesn’t become historic for the wrong reasons while Biden speaks.
So far no speech, interview or appearance has managed to quell concerns over the president's mental fitness, health and stamina.
Even as world leaders arrived here in Washington today, the split screen was an awkward one; with congressional Democrats on Capitol Hill holding meetings over the future of Biden’s candidacy.
Which means the president can’t afford to put a foot wrong tonight, or during his solo press conference on Thursday.
Would Democrats allow the chaotic optics of collectively calling on Biden to step out of the race once and for all, during a Nato summit - with Russia's President Vladimir Putin watching on?
We just don’t know.
Chris Mason
Political editor
The UK prime minister answered a couple of our questions on the tarmac just before we took off for the Nato summit in Washington DC.
Firstly, he was asked what his message was to Russian President Vladimir Putin:
"My message is very, very clear that this Nato summit is an opportunity for allies to stand together to strengthen their resolve, particularly in light of that appalling attack against Russian aggression," he said.
"I'm pleased to have the early opportunity to confirm and reaffirm Labour's strong support, unshakeable support for Nato. We are a founding member, it's now the 75th anniversary but this is an opportunity to send that message in relation to Russian aggression wherever.
"But that attack last week was appalling so that message is even more important than it was before."
He was then asked how soon the UK would spend 2.5% of national income on defence, a proportion Labour have promised but without putting a timeline on when they would deliver on the promise.
"The most important thing is to, at this Nato summit, recommit to our solidarity with and standing with Ukraine and discuss the practical plans for further action we can take together in relation to Russian aggression... In relation to defence more generally, we will carry out our strategic review to look at the challenges, the capabilities, and on the back of that make further plans.
"I am committed to that 2.5% within our fiscal rules. That strategic review needs to come first. But today, tomorrow and the next day is all about standing together with our allies, discussing practically how we provide further support to Ukraine, and send a very, very clear message to Putin that we will stand against Russian aggression wherever it is in the world.”