Ukraine remains on “an irreversible path” towards Nato membership, Keir Starmer has told Volodymyr Zelenskyy in a phone call that underlined the divide between Europe and the US over the future of the country. According to a Downing Street readout of the call with the Ukrainian president, Starmer stressed “the UK’s concrete support for Ukraine, for as long as it’s needed”. It went on: “He was unequivocal that there could be no talks about Ukraine without Ukraine. Ukraine needed strong security guarantees, further lethal aid and a sovereign future, and it could count on the UK to step up. “The prime minister reiterated the UK’s commitment to Ukraine being on an irreversible path to Nato, as agreed by allies at the Washington summit last year.” While Starmer’s sentiments are no more than a restatement of the UK’s longstanding position, one maintained by Labour and the Conservatives, the decision to speak to Zelenskyy and the strong language used has a fresh resonance after Donald Trump’s interventions this week. On Wednesday, the US president suddenly announced that he and Vladimir Putin had spoken at length and agreed to begin negotiations over a ceasefire in Ukraine. Trump said it was unlikely Kyiv would win back all its territory, and that he was “OK” with Ukraine not having Nato membership, a major concession to Moscow made before any formal talks have begun. The US defence secretary, Pete Hegseth, speaking at a Nato meeting in Brussels, also ruled out Ukraine’s membership of the alliance and the restoration of Crimea and other territories occupied by Moscow since 2014. The news prompted dismay in Ukraine and ebullience in Moscow at the apparent end of Russia’s isolation on the world stage. However, European defence ministers, who have gathered in Brussels for a Nato meeting this week, have pushed back hard against concessions to Russia. Boris Johnson, the UK former prime minister, said on Friday that Trump would not “betray” Ukraine, and that he had a “very, very good point” about Europe needing to step up, claiming there was “quite a lot of headless chicken-ism from the Europeans” about what the US was saying. In an interview with GB News, he said: “I think people need to focus more carefully on what the Trump administration is actually saying … what we should be doing is working with our European friends on the crucial part of the Trump proposals which is to fortify Ukraine. If we can’t get them immediately into Nato, what we need to do is strengthen them.” Speaking overnight, Emmanuel Macron said a peace deal would amount to “capitulation”, and that only Zelenskyy could negotiate on behalf of his country. Downing Street said Starmer and the Ukrainian president agreed in their call that the third anniversary of Russia’s invasion, in 10 days’ time, “would be an important moment to demonstrate international unity and support for Ukraine”. It continued: “The leaders also reflected on the prime minister’s visit to Kyiv last month, and the president updated on his plans at Munich Security Conference. They agreed to stay in close contact.” Shortly before the phone call, the UK Foreign Office imposed sanctions targeting figures working in the Russian government, including Pavel Fradkov, a defence minister, and Vladimir Selin, who leads an arm of the country’s ministry of defence. The Foreign Office said in a statement it also imposed sanctions on Artem Chaika, whose extractives company supports Russian state-owned business, and two entities linked to Russia’s nuclear energy corporation Rosatom.