Volodymyr Zelenskyy has arrived in Downing Street for talks with Keir Starmer and the Nato secretary general, Mark Rutte.
No 10 is hosting the Ukrainian president, who has been pressing western governments for more military support and the green light to fire long-range weapons into Russia.
Zelenskyy is also due to meet the French president, Emmanuel Macron, the Italian prime minister, Giorgia Meloni, and German chancellor, Olaf Sholz, within the next 24 hours, his office said.
A spokesperson for Starmer told reporters on Wednesday that the British PM would be “reiterating the UK’s ironclad support for Ukraine in the face of ongoing Russian aggression”.
Zelenskyy had been due to present a “victory plan” for the war to leaders in Germany this week, but the summit was postponed after the US president, Joe Biden, pulled out to manage the domestic response to Hurricane Milton.
Organisers of the summit have promised to reschedule but it is unclear whether it can take place before the US presidential election in November. A victory for Donald Trump, a military aid sceptic, could result in the US government withdrawing support from Kyiv.
Zelenskyy visited Starmer in Downing Street days after his election victory in July. During that trip, the Ukrainian president became the first foreign leader to address the cabinet since Bill Clinton in 1997.
The No 10 spokesperson told reporters there had been no change to the UK government’s position on authorising Ukraine to fire long-range Storm Shadow missiles at targets inside Russia.
Ukrainian officials have argued for months that the weapons are vital to weaken Russia’s ability to strike Ukraine and force it to move its strike capabilities further from the border. Nato members led by the US are concerned about the prospect of a direct confrontation with Russia.
In a joint appearance with Rutte in Kyiv last week, Zelenskyy said western governments were “dragging out” deliveries of long-range weapons.
“We need sufficient quantity and quality of weapons, including long-range weapons, that, in my opinion, our partners are already dragging out,” Zelenskyy said.
He also called on Nato members to take a more active role in helping his country to fend off Russian aerial attacks. “We will continue to convince our partners of the need to shoot down Russian missiles and drones,” Zelenskyy said, adding: “what works in the skies of the Middle East and helps Israel defend itself can also work in the skies of our part of Europe”.