The Prime Minister said his “driving purpose” over the last few days has been reuniting Ukraine and the US after their presidents clashed in the White House.
As Sir Keir Starmer gathers European leaders in London to forge a common position on ending the war in Ukraine, the Prime Minister said he is “working hard” to bring about a lasting peace in the war-torn eastern European country.
Ukraine’s President Volodymyr Zelensky will join Sir Keir at the summit alongside the leaders of other European countries, before he heads off to meet the King.
He travelled to the UK on Saturday after his Oval Office blowout with Donald Trump which created a divide between the US and its European Nato partners.
Sir Keir told the BBC’s Sunday With Laura Kuenssberg the encounter made him feel “uncomfortable”, adding: “Nobody wants to see that.”
The Prime Minister said: “The important thing is how to react to that. There are a number of different routes people could go down. One is to ramp up the rhetoric as to how outraged we all are or not.
“The other is to do what I did, which is roll up my sleeves, pick up the phone, talk to President Trump, talk to President Zelensky, then invite President Zelensky for an extensive meeting yesterday, a warm welcome, and then further pick up the phone to President Macron and President Trump afterwards.
“My driving purpose has been to bridge this, if you like, and get us back to the central focus.”
Sir Keir insisted he trusts both Mr Zelensky and Mr Trump, who he believes is motivated by a “lasting peace”.
At Lancaster House, a mansion near Buckingham Palace, the Prime Minister is expected to urge the leaders of 18 European countries to follow the UK in answering the US’s calls to boost defence spending.
Sir Keir told the BBC he is “working hard” to bring about three components of a lasting peace in Ukraine.
He said: “For me, the components of a lasting peace are a strong Ukraine to fight on, if necessary, to be in a position of strength; to negotiate a European element to security guarantees, and that’s why I’ve been forward-leaning on this about what we would do; and a US backstop.
“That’s the package, all three parts need to be in place, and that’s what I’m working hard to bring together.”
Sir Keir said he hopes he can build a “coalition of the willing” from the summit.
While Mr Trump’s America is the driving force behind brokering a peace with Russia, Sir Keir wants Europe to be ready to lead peacekeeping efforts should a deal be struck.
A security guarantee from the Americans is the subject of “intense” discussion, Sir Keir said.
The clash between Mr Trump and Mr Zelensky in the Oval Office was broadcast around the world on Friday, in which the US president claimed his counterpart was “gambling with world war three”.
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 was placed on ice.
Reports in the US media suggested Mr Trump was even considering halting all aid to Kyiv after the meeting, in which he and his vice-president, JD Vance, engaged in heated exchanges with Mr Zelensky.
Nick Thomas-Symonds, a Cabinet Office minister, told Sky News the UK would “continue to be an honest broker” in face of the threat and “continue to make the case that peace is made from a position of strength, not a position of weakness”.
European leaders soon rallied in a show of solidarity with Ukraine while Sir Keir tried to keep the peace.
The Prime Minister then welcomed Mr Zelensky to Downing Street on Saturday in a meeting described as “meaningful and warm” by the Ukrainian leader.
Chancellor Rachel Reeves, meanwhile, signed a loan agreement worth £2.26 billion 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 on Sunday, 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.
Conservative leader Kemi Badenoch said her “heart went out” to Mr Zelensky following his clash with Mr Trump.
She told Sunday With Laura Kuenssberg: “I watched it and I couldn’t believe what was happening, he was being humiliated.”
Ahead of the summit, she added: “If we don’t have an American security guarantee within Nato, if we lose them, we’re going to be spending a hell of a lot more (on defence).
“We need to make sure that America does not disengage, it is in their interest for peace now, if we all get dragged into an escalation, America will get dragged into it eventually.”
Liberal Democrat leader Sir Ed Davey said the UK must work towards boosting European defence spending, because the special relationship with the US is “under strain”.
“We can’t rely, unfortunately, as much as we have done on the United States,” he said as he called for Europe to spend more cash on rearming.
Both Mrs Badenoch and Sir Ed have said they do not think the offer of a state visit to Mr Trump should be rescinded.
