Nato members are not expected to set clear pre-conditions for Ukraine’s eventual membership to the military alliance in the face of caution from the US and Germany while the war with Russia continues. Ukraine wants clarity on when and how it can join the alliance after the war with Russia ends, believing that western military protection is the only way it can remain unthreatened by its neighbour. However, it looks instead likely to be offered closer integration with Nato and a stronger political declaration in favour of its membership in principle. As the US president, Joe Biden, met the UK prime minister, Rishi Sunak, in Downing Street on Monday, American and British officials emphasised that setting specific hurdles for Ukraine to clear was unrealistic given the uncertainty of the ongoing conflict. At the heart of Nato is article 5 of its founding charter, which states each member agrees “that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all”. It requires member states to join in defending the country under attack. Colin Kahl, the US undersecretary for defence, visiting London alongside the president, said there was resistance in the White House to any suggestion “that there’s a degree of automaticity or immediacy” to Nato membership. British sources concurred, although Downing Street said the UK wanted “to support Ukraine on a pathway to joining the alliance” ahead of a critical leaders’ meeting in the Lithuanian capital of Vilnius on Tuesday and Wednesday. Kyiv won a concession on Monday, with Nato members agreeing to eliminate formal requirements for it to sign up to a membership action plan, a formal pathway to membership that has taken other countries several years to complete. “I welcome this long-awaited decision that shortens our path to Nato” said Dmytro Kuleba, Ukraine’s foreign secretary, but he added the summit would be “the best moment to offer clarity on the invitation to Ukraine to become a member”. Negotiations on a final summit text were expected to continue into Monday evening, to agree what is expected to be a carefully constructed statement intended to go somewhat further than a previous commitment given to Ukraine in 2008, that the country could become a member at an indefinite point in the future. Jens Stoltenberg, Nato’s secretary general, emphasised that the summit would reach a consensus. “All allies agree that Ukraine will become a member of the alliance and I’m confident that the summit will make decisions which will be strong and positive on Ukraine,” he said at a press conference. But it appears that the UK, France and other Nato members in eastern Europe have found no way to persuade a cautious White House into a more specific membership commitment. On Sunday, Biden said Ukraine was “not yet ready” for Nato, and that the country would “take some time to meet all the qualifications”. Nato members are also expected to make further bilateral military aid commitments to Ukraine. On Monday, the UK announced it had agreed a £190m contract with BAE Systems to increase the production of 155mm Nato standard shells eightfold, many of which are expected to be given to Kyiv’s military. “We have also seen the Nato alliance come together like never before in support of Ukraine and with firm determination that Russia cannot succeed,” Sunak said as he announced the ammunition boost, adding: “That is work we need to continue this week.” However, a separate package of security guarantees for Ukraine, from the US, UK, Germany and France, is not now expected to be announced until the end of the summit at the earliest, amid last-minute wrangling. These are intended to commit the countries to providing military aid and economic support to Kyiv in the long term. Ukraine’s president, Volodymyr Zelenskiy, is expected to attend on Wednesday at an inaugural meeting of a Nato-Ukraine council designed to foster closer cooperation – having previously warned he may not attend at all if his membership pathway demands were not met. Downing Street also said that the UK would shortly publish a defence paper outlining further reforms to the armed forces, reflecting lessons learned from the Russian invasion of Ukraine. The document, expected to confirm greater investment in artillery and drones, is anticipated early next week. But Labour said the UK was one of the few Nato members heading into the summit without having revised its defence plans in the light of the Ukraine war. Its research found that 26 out of 31 Nato countries had recast their defence strategies, with Germany committing to spend an extra €100bn and Poland lifting spending to 4% of GDP. John Healey, the shadow defence secretary, said: “It’s embarrassing for the UK to go to the Nato summit as one of only five Nato nations that has not rebooted defence plans since President Putin invaded Ukraine.”