Sir Keir Starmer was set to fly to Washington on Thursday for talks with President Joe Biden as Ukraine warned it faces defeat unless it is allowed to fire Western missiles deeper into Russia.
Ukraine’s President Volodymyr Zelensky said he was counting on the allies to come up with “strong decisions” permitting the use of the long-range missiles to widen the offensive, after he deployed ground forces in Russia’s region of Kursk.
"We rely heavily on it, and frankly, we can't prevail without it," he said at a conference on Wednesday in Kyiv attended by Foreign Secretary David Lammy and US Secretary of State Antony Blinken.
Fearing a major escalation with Vladimir Putin, President Biden has so far vetoed allowing unrestricted use of the missiles by Ukraine.
But Mr Blinken said he had "no doubt" that the president and Sir Keir would discuss their expanded use when they meet at the White House on Friday, while Mr Lammy said the West was “listening carefully” to Ukraine’s needs.
The issue has taken on added urgency after what Mr Lammy called the “horrendous” transfer of ballistic missiles from Iran to Russia.
Mr Biden has allowed Ukraine to fire US-provided ATACMS missiles across the border into Russia in self-defence, but has largely limited the distance they can be fired.
The UK and European allies have taken their cue from the White House, and further discussions would be needed after Friday’s summit if the use of the missiles is to be expanded.
The Washington trip is the second by Sir Keir since he became PM, following one in July to mark Nato’s 75th anniversary that was also attended by Mr Zelensky. Then, Mr Biden caused consternation by mistakenly introducing the Ukrainian leader as “President Putin”.
Downing Street said there had been “no change in our position” on the use of UK-supplied Storm Shadow missiles into Russia, but reaffirmed that “we will always continue to listen to Ukrainians”.
“And the Prime Minister and (President) will be discussing our support and how we can best-support Ukraine at this critical juncture as we head into the winter,” a No10 spokeswoman said.
She added: “I’m not going to get into specifics of operational discussions and the details of that, not least because that would benefit Putin.”
Kremlin spokesman Dmitry Peskov said it appeared likely that the White House and allies had already agreed to allow greater use of the missiles. Russia’s response “will be an appropriate one”, he warned.
"The involvement of the United States of America and European countries in the conflict over Ukraine is direct, and each new step increases the degree of this involvement,” the Putin ally added.
Mr Lammy and Mr Blinken traveled together to the Ukrainian capital on a rare joint tour to underscore the UK-US commitment. Air-raid sirens sounded repeatedly during the visit, causing delays in their schedule and forcing them to cancel a wreath-laying ceremony.
With Ukraine’s forces under mounting strain after two-and-a-half years of war, the Foreign Secretary announced at least another £600 million of UK support.
Underscoring Britain’s “ironclad” support for Ukraine, Defence Secretary John Healey meanwhile announced that hundreds of extra air defence missiles, tens of thousands of artillery ammunition rounds and more armoured vehicles would be delivered by the end of the year.
Ukraine's air force said on Thursday that it had shot down 44 out of 64 drones launched by Russia overnight. Russian forces also used five missiles, it said.
Russian forces were also accused of attacking energy facilities and civilian infrastructure in the northeastern Ukrainian town of Konotop overnight.
The attack injured at least 13 people, according to local officials.
