The US and its closest allies are pursuing a multilateral agreement with Ukraine that will allow western powers to provide long-term security assurances to Kyiv, in lieu of a concrete promise of Nato membership for the war-torn country.

The so-called Quad — the US, UK, Germany and France — is working on an overarching political declaration with Ukraine, according to officials who declined to be identified given the sensitivity of the talks. They said that, under the umbrella declaration, Ukraine would conclude bilateral agreements formalising the current level of military and financial aid — and establish it on a more long-term footing with space to expand it if deemed necessary.

But neither the framework document nor the bilateral agreements would have the status of legal treaties and they would be signed outside the Nato alliance. Discussions are ongoing and a deal could be reached before Nato’s summit in Vilnius next month, officials said, while cautioning that there was no formal agreement between the western countries on a timeline.