Prime Minister Keir Starmer has landed in Washington DC ahead of talks with Donald Trump, Volodymyr Zelenskyy and other European leaders.
The conference follows the US president's meeting with Russian President Vladimir Putin in Alaska, where the Russian leader reportedly requested that Ukraine give up the Donetsk and Luhansk areas in exchange for the war's end.
The initiative has reportedly received private support from Mr Trump, a move Kyiv has fiercely opposed.
The night before the high-level meeting in the White House, Mr Trump implied that Ukraine could not reclaim Crimea, which Russia annexed in 2014, and placed the burden of concessions on Mr Zelensky.
Russia's refusal to stop fighting before accepting a deal would make any effort to achieve enduring peace more difficult, Ukraine's leader has warned.
Mr Zelensky stated in a statement prior to his journey that “stopping the killing is a key element of stopping the war.”
Sir Keir and other leaders “stand ready to support this next phase of talks,” according to Downing Street, and they will emphasise that they will continue to help Ukraine “as long as it takes.”
Russia's demand that Ukraine give up Donetsk and Luhansk is one of the territorial issues that are anticipated to be discussed during today's negotiations.
They are also anticipated to discuss Ukraine's security assurances, which may be supported by US air power.
Along with sanctions pressure on Russia, the role of Nato and European allies in ensuring a settlement is probably going to be debated.
Leaders in Europe also want to guarantee that Ukraine is included in all talks.
This will mark one of the most important visits Sir Keir has embarked on this year. Here are all the other trips the prime minister has taken this year.
Kyiv, Ukraine visit
In an attempt to strengthen support for Kyiv, Sir Keir made his first trip to the war-torn nation and inked a century-long alliance with Ukraine back in January.
As he reaffirmed European solidarity against Russian aggression, Sir Keir said the 100-year agreement was the foundation of Britain's “steadfast support” for Ukraine.
The prime minister took an overnight train from the Polish border to Kyiv, where he met Ukrainian President Volodymyr Zelenskyy.
Sir Keir met patients and workers at a burns hospital, and the two placed a wreath on the wall honouring fallen soldiers.
Sir Keir said: “Putin's ambition to wrench Ukraine away from its closest partners has been a monumental strategic failure. Instead, we are closer than ever and this partnership will take that friendship to the next level.
“The power of our long-term friendships cannot be underestimated. Supporting Ukraine to defend itself from Russia's barbaric invasion and rebuild a prosperous, sovereign future, is vital to the government's security and Plan for Change.”
Auschwitz
During a visit to Poland to meet with its political leaders, the prime minister lay a wreath at the former Nazi concentration camp in advance of the 80th anniversary of its liberation.
After he and his wife Victoria, who is Jewish, visited the site, Sir Keir said in a statement: “Nothing could prepare me for the sheer horror of what I have seen in this place. It is utterly harrowing. The mounds of hair, the shoes, the suitcases, the names and details, everything that was so meticulously kept, except for human life.”
He also visit Warsaw for talks with his Polish counterpart Donald Tusk about a new defence and security treaty between the two countries.
Brussels trip
Sir Keir went to Brussels to join a gathering of European Union leaders – the first time a British prime minister has done so since Brexit.
The prime minister headed over the English Channel for talks focused on defence and security co-operation and also met Nato secretary general Mark Rutte whilst there.
The trip was also part of what he called a “reset” between the UK and the European Union.
A visit to Paris
Sir Keir went to Paris for emergency talks with fellow leaders on Ukraine after he warned of a “generational challenge” and said the UK and Europe “need to do more” on security.
He has stated that if an agreement to stop the war with Russia could be reached, he would be willing to send a peacekeeping force into Ukraine.
The conference took place amid concerns that the US may scale back its security commitments in the continent and as European leaders were frantically trying to come up with a plan in response to US President Donald Trump's desire for an agreement with Russian President Vladimir Putin.
First visit to Washington to meet Trump
Sir Keir met US President Donald Trump during his first visit to the White House.
The visit had so many interesting elements.
The opening included the prime minister reaching inside his jacket pocket and pulling out an official letter from King Charles III - an invitation for a second state visit.
Trump appeared to be genuinely taken back for a few seconds, asking: “Am I supposed to read it right now?” and after taking a minute to read the letter, Trump said he accepted the invitation.
Sir Keir also couldn’t help but clash with US Vice President JD Vance over free speech.
A week earlier, US Vice President JD Vance had criticised the UK and other European democracies at the Munich Security Conference, saying that "free speech is in retreat."
Trump urged his deputy to defend himself when he was questioned about the remarks. Mr Vance maintained that “there have been infringements on free speech that actually affect not just the British” but moreover “American technology companies and by extension, American citizens”.
Sir Keir interrupted and said: “We've had free speech for a very, very long time in the United Kingdom - and it will last for a very, very long time.”
He rejected Vance's claim, saying “in relation to free speech in the UK, I'm very proud of our history there”.
Paris, again
Sir Keir visited Paris again in March to rebuild trust and coordination between the UK and EU following years of tense Brexit fallout. Discussions reportedly included security, trade, energy, and migration cooperation.
Talks with President Emmanuel Macron focused on bilateral defence cooperation, especially in light of the war in Ukraine and increasing European calls for strategic autonomy. Follow-up to the UK-Poland defence pact and the Ukraine summit hosted in London earlier that month.
Although not an EU member, Sir Keir is a proponent of closer strategic alignment. His Paris visit likely included talks around broader European Political Community (EPC) initiatives, where the UK now has observer or contributor status.
