European nations must play a “full part” in ensuring Ukraine’s security in the event of a peace agreement with Russia, Sir Keir Starmer has said.
The prime minister said Europe needed to “step up” its defence capabilities in the face of a “generational” security challenge Moscow poses.
Sir Keir’s remarks came ahead of his arrival in Paris for a summit of European leaders to discuss concerns over the US-Russia talks on ending the war.
He is expected to urge his counterparts to commit troops to a peacekeeping force in a potential peace deal, after writing that he was “ready and willing” to put UK soldiers on the ground in Ukraine to help guarantee its safety.
“We need to step up in terms of our collective response in Europe, and by that I mean capability,” Sir Keir said ahead of the meeting at the Élysée Palace.
“By that, I mean playing our full part when it comes to the defence of the sovereignty of Ukraine if there’s a peace agreement.”
US President Donald Trump has long called on European allies to increase their defence spending. The hastily convened discussions in Paris are taking place days after his defence secretary, Pete Hegseth, said Europe will have to be primarily responsible for guaranteeing its own security going forward.
The EU’s foreign policy chief, Kaja Kallas, told the BBC earlier this month that Trump was right to criticise Europe’s spending.
“To prevent the war, we need to spend more, that is clear,” she said.
Sir Keir will later say this requires “further supporting Ukraine’s military” as well as “being ready to contribute to security guarantees by putting our own troops on the ground if necessary”, a Downing Street spokesman said.
Writing in the Telegraph on Monday, Sir Keir said he was willing to send British troops to Ukraine as part of a multinational force to police the border between Ukrainian-held and Russian-held territory.
But experts say to do so effectively would be a massive undertaking that would require a large increase in defence spending.
Malcolm Chalmers, deputy director of the Royal United Services Institute, said that, unlike UN peacekeeping forces that are there to observe, if the force being proposed is intended to deter Russian attacks, “it’s a whole different matter altogether”.
“You need credible, well-armed forces – and you not only need frontline forces, you need backup forces, and air forces, and so on,” he told the BBC. “That’s a much bigger ask.”
General Sir Adrian Bradshaw, a former Nato commander, said: “This cannot be a token force, it cannot be something that observes bad behaviour and stands on the sideline.”
He told BBC Radio’s World at One that it would have to do “effectively what Nato does on its own turf – really deter aggression”, and would need to be “underpinned by a grand strategy for containment of Russia” that would make clear any future conflict would not be contained to Ukraine.
“Essentially, the force needs to be large enough to defeat an incursion,” he added.
The former head of the British Army, Lord Dannatt, previously estimated such a force would need around 100,000 troops – with the UK contributing about two-fifths.
“We just haven’t got that number available,” he said on Saturday, adding that getting the military into shape to perform this role would come at a considerable cost.
The UK currently spends around 2.3% of its total economic output on defence. The government has committed to increasing defence spending to 2.5%, but has not said when this will be achieved.
Sir Keir earlier told reporters that the government would set out a path to meeting the 2.5% commitment once it finishes its strategic defence review.
“Part of my message to our European allies is that we’ve all got to step up on both capability and on spending and funding,” he said.
“That includes the UK, which is why I’ve made that commitment to spend more.”
Monday’s summit appears to have been spurred by the Trump administration’s decision to initiate peace talks with Russia – due to start in Saudi Arabia on Tuesday.
US officials have suggested European nations, including Ukraine, would be consulted on peace talks with Russia, but not directly involved in them.
Ukrainian President Volodymyr Zelensky has said Kyiv did not know about the talks and would not recognise any agreement made without its involvement.
Sir Keir has joined the leaders of France, Germany, Italy, Poland, Spain, the Netherlands and Denmark, the presidents of the European Council and European Commission, and Nato Secretary General Mark Rutte.
European leaders have also expressed concern after Hegseth said last week that it was “unrealistic” to expect Ukraine will return to its pre-2014 borders – before Russia annexed Crimea and took parts of the nation’s south and east in its 2022 full-scale invasion.
Hegseth also downplayed the prospect of Ukraine joining the mutual defence alliance Nato – something Sir Keir has said it was on an “irreversible” path towards.
Gen Sir Bradshaw noted these potential concessions to Russia, and said: “If we can’t return Ukraine to what it was as a sovereign nation before this war – we have absolutely got to make it a lasting peace.”
The prime minister is due to meet Trump next week, No 10 has confirmed. On Sunday, a minister said the UK could serve as a “bridge” between the US and Europe.
Polish Prime Minister Donald Tusk has already indicated his nation would not send troops into Ukraine, but would continue to support it with military, financial and humanitarian aid.
Meanwhile, fighting on the ground in Ukraine continued over the weekend, with at least three civilians killed in Russian strikes on Sunday, according to local authorities.
Several areas of Ukraine are under an emergency blackout following attacks on energy infrastructure, while Russia’s defence ministry said it intercepted and destroyed 90 Ukrainian drones on Sunday night.