Sir Keir Starmer will speak to western allies on Sunday ahead of Volodymyr Zelensky’s White House meeting with Donald Trump.
The Prime Minister, France’s Emmanuel Macron and Germany’s Friedrich Merz will host the meeting of the coalition of the willing on Sunday afternoon.
Mr Zelensky will fly to Washington DC on Monday, where he will meet the US president for the next stage of talks.
The one-on-one in the Oval Office could pave the way for a three-way meeting alongside Russian leader Mr Putin, the US president has said.
The coalition of the willing, made up of 30-plus nations, is prepared to deter Russian aggression by putting troops on the ground in Ukraine once the war is over.
The meeting, which is expected to take place at approximately 2pm UK time, comes on the heels of Mr Trump’s summit in Alaska with his Russian counterpart Vladimir Putin.
Mr Trump hoped to secure a peace deal from the talks at a military base in Anchorage, but both he and Mr Putin walked away without agreement on how to end the war in Ukraine.
The US leader, however, insisted “some great progress” was made, with “many points” agreed and “very few” remaining.
Several news outlets have cited sources which claimed that during the negotiations Mr Putin demanded full control of Donetsk and Luhansk – two occupied Ukrainian regions – as a condition for ending the war.
In exchange he would give up other Ukrainian territories held by Russian troops.
Other outlets reported that Mr Trump is inclined to support the plan, and will speak to Mr Zelensky about it on Monday when they meet in the Oval Office.
After the Alaska summit, the US president told Fox News it was now up to the Ukrainian to “make a deal” to end the war.
Sir Keir commended Mr Trump’s “pursuit of an end to the killing” following a phone call with the US president, Mr Zelensky and Nato allies on Saturday morning.
But he insisted Ukraine’s leader must not be excluded from future talks to broker a peace in Ukraine.
The Prime Minister and European leaders appeared increasingly confident that Mr Trump will offer a “security guarantee” of air support to back up allied troops on the ground in Ukraine.
The Prime Minister welcomed “the openness of the United States, alongside Europe, to provide robust security guarantees to Ukraine as part of any deal”.
“This is important progress and will be crucial in deterring Putin from coming back for more,” he added.
But Mr Trump also appeared to have a change of heart on what he wants to achieve from the talks, indicating that he wants a permanent peace settlement rather than a ceasefire.
Writing on his Truth Social platform, the US president said: “It was determined by all that the best way to end the horrific war between Russia and Ukraine is to go directly to a peace agreement, which would end the war, and not a mere ceasefire agreement, which often times do not hold up.”
Mr Putin described the meeting as “timely” and “useful” after leaving Alaska.
Experts have warned the face-to-face summit has risked legitimising the Russian leader, after he has been made a pariah by the international community for years.
Dr Neil Melvin, director of international security at the Royal United Services Institute (Rusi), said: “Vladimir Putin came to the Alaska summit with the principal goal of stalling any pressure on Russia to end the war.
“He will consider the summit outcome as mission accomplished.”
I received a report from Commander-in-Chief Oleksandr Syrskyi. The front, the defense of positions, and up-to-date information on the intentions and movements of the Russian army. We are defending our positions along the entire front line, and for the second day in a row, we have…
— Volodymyr Zelenskyy / Володимир Зеленський (@ZelenskyyUa) August 16, 2025
Ukraine’s president Mr Zelensky warned Russia may ramp up its strikes against his country in the coming days “in order to create more favourable political circumstances for talks with global actors”.
Kyiv’s troops are “defending our positions along the entire front line”, he added on social media site X.
Mr Zelensky had earlier insisted a ceasefire must include an end to fighting on land, in the sea and the air, as well as the return of all prisoners of war and captured civilians, including children.
Sanctions on Moscow “should be strengthened if there is no trilateral meeting or if Russia tries to evade an honest end to the war”, Mr Zelensky added.
