Keir Starmer will co-chair a meeting with pro-Ukraine allies on Wednesday.
It comes after a call with US President Donald Trump and European leaders about ending Ukraine’s war against Russia.
Sir Keir will join a virtual call at midday with Ukrainian President Volodymyr Zelensky, French President Emmanuel Macron and German Chancellor Friedrich Merz.
They will then be joined by Mr Trump and US vice president JD Vance.
Later, the Prime Minister will co-chair a Coalition of the Willing meeting to update wider partners on the day’s discussions.
The Coalition of the Willing is an international effort to support Ukraine towards a lasting peace, led by the UK, France and Ukraine.
It is made up of 31 countries that have pledged strengthened support for Kyiv, including 27 European countries, as well as Canada, Australia, New Zealand and Japan.
Ahead of Wednesday’s call, a Downing Street spokesperson said: “The Prime Minister remains absolutely focused on a solution to this conflict grounded in Ukraine’s national interests.
“He is determined to achieve a just and lasting peace in Ukraine, backed by robust and credible security guarantees that will deter Russia from threatening Ukraine in future.”
This comes ahead of the expected meeting between Mr Trump and Russian President Vladimir Putin in Alaska on Friday.
The two leaders are set to meet to discuss the future of the Kremlin’s invasion, without the presence of Mr Zelensky.
The Ukrainian President said at a news briefing on Tuesday that Mr Putin wants Ukraine to withdraw from the remaining 30 per cent of the Donetsk region that Kyiv controls as part of a ceasefire deal.
This was conveyed to him by US officials, Mr Zelensky explained.
However, he reiterated that Ukraine would not withdraw from territories it controls because it is unconstitutional and would only serve as a springboard for a future Russian invasion.
Mr Trump has also signalled he thinks Ukraine might need to cede territory in order to end the conflict, stating there is likely to be “some land-swapping going on”.
Speaking during a lengthy press conference on Monday, Mr Trump pledged to “try to get back” some of Ukraine’s “oceanfront property” from Russia.
He said: “We’re going to change the lines, the battle lines. Russia has occupied a big portion of Ukraine. They’ve occupied some very prime territory. We’re going to try and get some of that territory back for Ukraine.
“They have taken largely – in real estate we call it oceanfront property. That’s always the most valuable property.”
A statement released by the European Union on Tuesday read: “A just and lasting peace that brings stability and security must respect international law, including the principles of independence, sovereignty, territorial integrity and that international borders must not be changed by force.
“The people of Ukraine must have the freedom to decide their future.
“The path to peace in Ukraine cannot be decided without Ukraine.
“Meaningful negotiations can only take place in the context of a ceasefire or reduction of hostilities.”
In response, Mr Zelensky said on X (formerly Twitter): “I am grateful to the leaders of Europe for their clear support for our independence, territorial integrity, and precisely such an active approach to diplomacy that can help end this war with a dignified peace.
“Indeed, We all support President Trump’s determination, and together we must shape positions that will not allow Russia to deceive the world once again.
“We see that the Russian army is not preparing to end the war. On the contrary, they are making movements that indicate preparations for new offensive operations.
“In such circumstances, it is important that the unity of the world is not threatened.
“As long as they continue the war and the occupation, all of us together must maintain our pressure – the pressure of strength, the pressure of sanctions, the pressure of diplomacy.”
