Keir Starmer is gathering European leaders and Volodymyr Zelensky in London today as they scramble to respond to the Oval Office meltdown.
France’s Emmanuel Macron and Italy’s Giorgia Meloni are among those assembling to consider how to shore up Nato and the continent’s defences from Russian aggression.
The summit was already planned before the extraordinary on-camera slanging match between Donald Trump, his vice president JD Vance and Mr Zelensky.
Mr Trump is said to be demanding a public apology from the Ukrainian amid threats to pull the plug on US military support. In a sign he is keen to mend fences with the US, Mr Zelensky has described the president’s support for Ukraine as ‘crucial’.
There have been calls for Mr Trump’s invite for an unprecedented state visit to the UK to be withdrawn, although No10 is adamant that will not happen.
European leaders have been voicing solidarity with Mr Zelensky, who was warmly embraced by Sir Keir in Downing Street last night, as they try to find a way of repairing relations.
They are also racing to fill the potential gap in European defences from the abrupt withdrawal of the world’s largest military and economic power.
Sir Keir is positioning himself as a bridge between Europe and Mr Trump after his successful visit to the White House last week.
In the opulent surroundings of Lancaster House, near Buckingham Palace, the PM will urge the 18 countries in attendance to boost defence spending.
He is expected to tell leaders they are ‘at a turning point’, and must recognise the ‘brutal reality’ and start taking action instead of making ‘carefully crafted speeches’.
In comments briefed ahead of the summit, Sir Keir said: ‘Today I will reaffirm my unwavering support for Ukraine and double down on my commitment to provide capacity, training and aid to Ukraine, putting it in the strongest possible position.
‘In partnership with our allies, we must intensify our preparations for the European element of security guarantees alongside continued discussions with the United States.
‘We have an opportunity to come together to ensure a just and lasting peace in Ukraine that secures their sovereignty and security. Now is the time for us to unite in order to guarantee the best outcome for Ukraine, protect European security and secure our collective future.’
Sir Keir pledged this week to raise the UK’s defence spending to 2.5 per cent of GDP by 2027, slashing the aid budget to free up the funding.
Chancellor Rachel Reeves is also expected to cut £5billion from welfare and allow the £28billion national wealth fund to be invested in defence projects.
The summit comes after several days that saw the foundations of the Nato alliance – that has helped avoid world war for 80 years – shaken.
The clash between Mr Trump and Mr Zelensky in the Oval Office was broadcast around the world on Friday, with the US President accusing his counterpart of ‘gambling with World War Three’ after Russia invaded.
It resulted in Ukraine’s president being kicked out of the White House and a deal to exchange mineral rights for further US military support put on ice.
Mr Trump said he would not be welcome until he was willing to talk about ‘peace’.
Reports in the US media suggested Mr Trump was even considering halting all aid to Kyiv after the meeting.
European leaders have rallied in a show of solidarity with Ukraine, while Sir Keir has repeatedly spoken to both presidents over the phone.
The PM welcomed Mr Zelensky to Downing Street yesterday in a meeting described as ‘meaningful and warm’ by the Ukrainian leader.
The two men embraced as they met, and again later as they parted, and Sir Keir took the unusual step of walking Mr Zelensky to his car, instead of waving him goodbye from the front step of No10.
Ms Reeves has signed a loan agreement worth £2.26billion with her Ukrainian counterpart, to pay for further military support and the rebuilding of Ukraine in future.
The UK hopes to recoup the costs from frozen Russian assets locked in bank accounts across Europe.
Mr Zelensky is expected to meet the King at his Sandringham estate in Norfolk this evening after attending the summit.
The embattled Ukrainian leader meets Charles days after Mr Trump was offered an unprecedented second state visit to the UK as part of a charm offensive aimed at winning the US president’s support.
Sir Keir spoke to Mr Trump last night for the second evening in a row, as well as French President Emmanuel Macron, as he seeks to be a bridge across the Atlantic and smooth out the ongoing division between Western allies.
Mark Rutte, Nato secretary general, told the BBC he urged Mr Zelensky to repair his relationship with the US president in a Friday-night phone call, as the alliance’s members ‘need to stick together’ against Russia.
Conservative leader Kemi Badenoch warned in a Telegraph newspaper article that America’s commitment to Europe ‘cannot now be taken for granted’, after urging Sir Keir to push for ‘concrete’ pledges during the summit.