The UK and Ukraine have signed a loan agreement worth £2.26 billion (€2.74 billion) to support Kyiv's defence capabilities, which London called a sign of "unwavering and ongoing support for the Ukrainian people".
The two countries' finance ministers, Rachel Reeves and Sergii Marchenko, signed the loan at a virtual ceremony as British Prime Minister Keir Starmer met Ukrainian President Volodymyr Zelensky in Downing Street.
It is to be to be paid back with the profits of immobilised sovereign Russian assets.
The Ukrainian president said the funds "will be directed toward weapons production in Ukraine".
Mr Zelensky said he had "important and warm" talks with Mr Starmer, with a discussion following a row between the Ukrainian leader and the US President Donald Trump yesterday.
He added discussions with the UK prime minister regarded strengthening Ukraine's position and obtaining reliable security guarantees.
"During our talks we discussed the challenges standing before Ukraine and all of Europe, coordination with our partners, concrete steps to strengthen Ukraine's position and ending the war in a just fashion, with reliable security guarantees," he wrote on the Telegram messaging app.
Mr Starmer greeted Mr Zelensky with an embrace upon his arrival at Downing Street as a crowd cheered.
"I hope you heard some of that cheering in the street. That is the people of the United Kingdom coming out to demonstrate how much they support you ... and our absolute determination to stand with you," Mr Starmer said to Mr Zelensky.
Mr Starmer told Mr Zelensky he had "full backing across the United Kingdom", adding "we stand with you and Ukraine for as long as it may take".
Mr Zelensky's talks with Mr Starmer were held before a summit of European leaders that the Ukrainian president will attend tomorrow to discuss a peace plan for Ukraine.
Other European leaders also issued messages of support for Mr Zelensky and Ukraine after his meeting with Mr Trump, highlighting differences between traditional allies the United States and Europe over the war since Mr Trump returned to office.
Mr Starmer spoke to both Mr Trump and Mr Zelensky yesterday and French President Emmanuel Macron also visited Mr Trump in Washington this week.
Mr Zelensky is also due to meet Britain's King Charles tomorrow.
Britain's Sun newspaper said the meeting would take place at the monarch's Sandringham estate in eastern England.
"I'm very happy that His Majesty the King accepted my meeting tomorrow," Mr Zelensky told the UK prime minister at the start of their meeting.
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Britain has been a vocal backer of Ukraine and King Charles has previously expressed his support for the Ukrainian president, speaking of the "determination and strength" of the Ukrainian people in the face of an unprovoked attack from Russia.
During Mr Starmer's visit to the White House, he presented Mr Trump with a written invitation from the king for a state visit, which would make the US president the first elected political leader in modern times to be hosted for two state visits by a British monarch.
'New age of infamy'
Yesterday's heated exchange between Mr Zelensky and Mr Trump sent alarm bells ringing across Europe, with Germany branding it the start of a "new age of infamy", while Russia reacted gleefully to Mr Trump's apparent takedown of Mr Zelensky.
Mr Zelensky has since insisted that Mr Trump's support is still "crucial" for Ukraine despite the row with the US president.
"It's crucial for us to have President Trump's support. He wants to end the war, but no one wants peace more than we do," Mr Zelensky said in a post on social media platform X.
European leaders rallied to the Ukrainian leader's defence, with Polish Prime Minister Donald Tusk saying Ukraine was "not alone".
Others pressed for an olive branch.
In an interview with the BBC, NATO chief Mark Rutte said that he talked to Mr Zelensky and told him he had to "find a way" to restore his relationship with Mr Trump after the dispute.
Shouting match
The US president stunned many in Europe when he reached out to Russian President Vladimir Putin to seek a deal on Ukraine, which Moscow invaded three years ago.
The Republican's sudden shift on Ukraine, sidelining Kyiv and Europe while pursuing rapprochement with Mr Putin, has rattled the transatlantic NATO alliance.
Those concerns were only exacerbated by the scene that played out in the White House, where the years-long US policy of support for Ukraine collapsed in a shouting match.
During the televised clash, Mr Trump and Vice President JD Vance shouted at Mr Zelensky, accusing him of not being "thankful" and refusing to accept their proposed truce terms.
"You're either going to make a deal or we're out, and if we're out, you'll fight it out and I don't think it's going to be pretty," Mr Trump said.
Though he refused to apologise, the day after Mr Zelensky indicated that he was still open to signing the deal on Ukraine's mineral wealth coveted by Mr Trump, insisting that "despite the tough dialogue" Ukraine and the United States "remain strategic partners".
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'Insolent pig'
Former Russian president Dmitry Medvedev called Mr Zelensky an "insolent pig" who had received "a proper slap down" following the row.
Mr Zelensky's Washington trip was a "complete failure", Moscow said.
Passers-by on the streets of Moscow welcomed Mr Trump's war of words with his Ukrainian counterpart.
"Frankly speaking, it was very pleasing that (Zelensky) got such a rebuke in the White House," nursery worker Galina Tolstykh told AFP.
EU 'independence' from US
Mr Trump alarmed Kyiv and European allies with his abrupt U-turn in US policy, casting himself as a mediator between Mr Putin and Mr Zelensky and refusing to condemn the Russian invasion.
He said in the Oval Office that he had "spoken on numerous occasions" to Mr Putin - more than has been publicly reported.
With fears over whether the United States will continue to support NATO mounting, tomorrow's gathering in the UK will also address the need for Europe to increase defence cooperation.
French President Emmanuel Macron has said he is ready to "open the discussion" on a possible future European nuclear deterrent.
Germany's likely next leader, Friedrich Merz, also stressed the need for the continent to move quickly to "achieve independence" from the United States on defence matters.
But Hungarian Prime Minister Viktor Orban - the closest ally of Mr Trump and the Kremlin in the European Union - vowed to oppose a bloc-wide agreement on the conflict at the upcoming gathering.
"I am convinced that the European Union - following the example of the United States - should enter into direct discussions with Russia on a ceasefire and a sustainable peace in Ukraine," Mr Orban wrote in a letter.
Meanwhile, Russia's assault on Ukraine continued.
Russia said it has seized two more villages in the south of the eastern Donetsk region.
