Keir Starmer denies Joe Biden is 'senile' and insists he was 'on really good form' and 'mentally agile' during their hour-long chat - as new PM wades into US row over President's fitness to run for re-election

Keir Starmer waded into the row over Joe Biden's fitness to run for reelection today as he denied the president is 'senile'.

The PM insisted Mr Biden had been on 'really good form' and 'mentally agile' during their hour-long chat in the White House last night.

The comments, in a round of interviews with broadcasters in Washington this afternoon, came with controversy raging over Mr Biden's age.

Even some Democrats have been urging the 81-year-old not to run again after a disastrous TV debate against Mr Trump.

Downing Street has posted a behind-the-scenes video of Sir Keir chatting with Mr Biden face to face for the first time at the NATO summit.

The US commander-in-chief described the UK as the 'transatlantic knot' binding the two continents, backing Sir Keir's Brexit renegotiation by suggesting Britain should be 'closer to Europe'. 

At one point Mr Biden, who is facing questions over whether he is too old to stand for another term, slowly extended his hand towards Sir Keir. But he had to prompt the premier to take it - saying 'gimme your hand pal'.

Sir Keir told reporters earlier that Labour's manifesto plan to force members of the House of Lords to retire at 80 did not imply other octogenarian politicians such as Mr Biden should quit.

Asked by the BBC if Mr Biden was 'senile', Sir Keir replied: 'No, we had a really good bilateral yesterday, we were billed for 45 minutes, we went on for the best part of an hour, we went through a huge number of issues. At pace - he was actually on really good form.'

Pressed whether the president was 'mentally agile', the PM replied: 'Absolutely across all the detail. 

'We were going at pace through a number of issues, which was really important to me, because obviously, it was my first opportunity to have a bilateral like that. 

'And he showed incredible leadership.'

Sir Keir was asked whether it was 'unfair' that long-term supporters such as Hollywood star George Clooney were suggesting Mr Biden is 'not up to it'.

'Well, I'm giving you my readout of the meeting... as I say, we've covered a lot of ground strategic ground international stuff, and not just Ukraine. 

'He was on good form. And, of course, you know, various interventions yesterday, we went straight from that, to the dinner that he hosted.'

At the start of their meeting, Mr Biden said: 'I kind of see you guys as the knot tying the transatlantic alliance together, the closer you are with Europe. We know where you are, you know where we are.'

Sir Keir told the president: 'The special relationship is so important. It's forged in difficult circumstances, endured for so long, and stronger now than ever.

'I'm very pleased to be able to come so early in government to recommit to NATO, to recommit to the special relationship and to discuss these affairs with you.'

Boris Johnson has been among those warning that Labour will water down the terms agreed with the EU.  

A UK Government spokesman said Mr Biden and Sir Keir 'agreed we must continue to do whatever it takes to support Ukraine and ensure aggressors like Putin do not win'.

The spokesman added: 'The President welcomed the Prime Minister's recent comments on establishing closer relationships with our European counterparts, as well as the UK's commitment to Aukus.'

Speaking before the talks, Sir Keir tried to dodge questions about Mr Biden's age.

'In terms of the age in the House of Lords, the simple fact is that our House of Lords is massive,' he said.

'It's the second biggest political chamber in the world. I think it's only the Chinese who have a bigger political chamber than our House of Lords, we have to reduce it.

'That is the primary driver of the retirement at 80. You can see why that needs to be done. We've got 800-plus members of the House of Lords, it's simply too big. We need to reduce it.

'So it doesn't reflect on how other elected representatives are chosen in other countries, it's to do with the size of the House of Lords.'

Mr Biden is facing calls from some Democrats to step aside. He has vowed to fight on but commentators have warned his performance at the NATO summit could decide his fate.

The meeting came as Sir Keir prepared to urge NATO allies to support Ukraine for 'as long as it takes' as he confirmed the UK's own £3 billion a year military aid for Kyiv will continue.

The PM, who met Ukraine's President Volodymyr Zelensky in the margins of the NATO summit in Washington yesterday, will tell members of the alliance later that they need to send a 'clear message' to Russian leader Vladimir Putin.

The UK's military support for Ukraine will continue until at least 2030/31 and for as long as it is needed.

At a special session on Ukraine at the NATO summit, Sir Keir will warn that the frontline defence of the Euro-Atlantic region is the Ukrainian trenches.

He will say: 'NATO was founded by the generation who defeated fascism. They understood not just the value of our strength, but the strength of our values.

'Those values are under attack once again. Putin needs to hear a clear message ringing out from this summit – a message of unity and determination, that we will support Ukraine with whatever it takes, for as long as it takes, to uphold our shared values and our shared security.'

The Washington summit cemented Ukraine's 'irreversible' progress towards NATO membership, with a joint statement by the allies.

But because of NATO's Article V, which commits to mutual defence, the allies will not allow Ukraine to join while it is still at war as that would trigger an immediate conflict with Russia.

NATO allies are stepping up commitments on Ukraine while they await the results of November's US presidential election, where Donald Trump has threatened to reduce American support.

Concerns about Mr Biden's plan to run for re-election were evident during his Oval Office meeting with Sir Keir.

The president did not directly respond to questions about George Clooney's criticism, after the actor and prominent Democrat supporter suggested he should leave the race.