Volodymyr Zelenskyy will hold talks with Rishi Sunak today during a surprise visit to the UK.
The Ukrainian president said he was flying to London to meet “my friend Rishi”.
The pair will discuss the military help the UK is providing to Kyiv to help in the war with Russia.
“The UK is a leader when it comes to expanding our capabilities on the ground and in the air,” Zelenskyy said in a tweet.
“This cooperation will continue today. I will meet my friend Rishi. We will conduct substantive negotiations face-to-face and in delegations.”
The pair will meet Chequers, the PM’s official country residence.
Sunak will confirm the UK is providing further unmanned aerial systems to Ukraine, including hundreds of new long-range attack drones with a range of over 200km.
Sunak said: “This is a crucial moment in Ukraine’s resistance to a terrible war of aggression they did not choose or provoke.
“They need the sustained support of the international community to defend against the barrage of unrelenting and indiscriminate attacks that have been their daily reality for over a year.
The trip comes just days after defence secretary Ben Wallace confirmed the UK is providing Ukraine with long-range Storm Shadow cruise missiles.
The British-French air-launched missile has a range over over 155 miles and would allow Ukraine to strike deep into areas of the country currently occupied by Russia.
Wallace said: “Storm Shadow is a long-range, conventional-only, precision-strike capability. It complements the long-range systems already gifted, including Himars and Harpoon missiles, as well as Ukraine’s own Neptune cruise missile.”
He added: “The donation of these weapons systems gives Ukraine the best chance to defend themselves against Russia’s continued brutality, especially the deliberate targeting of Ukrainian civilian infrastructure, which is against international law.
The defence secretary said “Ukraine has a right to be able to defend itself against this”.
On Friday Sunak condemned the decision by Eurovision bosses to turn down Zelenskyy’s request to speak at the final of the contest.
The event was held in Liverpool because Ukraine - which won last year - was unable to host it.
Zelenskyy had asked to address the audience via video link, but was turned down by organisers, who said it must remain “non-political”.
But a spokesperson for Sunak said: “The values and freedoms that President Zelenskyy and the people of Ukraine are fighting for are not political, they’re fundamental, and Eurovision themselves recognised that last year when they rightly suspended Russia’s participation from the competition,” he said.
The spokesperson added: “The prime minister thinks it would be fitting for President Zelenskyy to address the event, given that we’re hosting it on behalf of Ukraine.”