Russia is preparing a new air assault with jets and attack helicopters to support its offensive in Ukraine, western intelligence has warned.

A build-up of fixed-wing and rotary aircraft have been spotted on Russia’s border with Ukraine leading analysts to believe Moscow could attempt to use the air assets to gain the initiative in the eastern Donbas region.

The warning came as more than 50 of Ukraine’s western allies gathered at Nato’s headquarters in Brussels to set out plans for future military support. Lloyd Austin, the US defence secretary, who convened the talks, said there had been no breakthrough on supplying Kyiv with fighter jets.

Oleksiy Reznikov, Ukraine’s defence minister, even showed journalists a handkerchief with a picture of a fighter jet on it ahead of the meeting where he appealed for combat aircraft. But in private talks with his counterparts, he said accelerating deliveries of air defence and artillery systems, as well as armour, were more important for Ukraine’s army.

“The Russian land forces are pretty depleted so it’s the best indication they will turn this into an air fight,” a senior US administration official said. “If the Ukrainians are going to survive they need to have as many air defence capabilities and as much ammunition as possible.” \

In the talks, Austin warned that Russia’s air force still posed a significant threat to Ukraine.

A senior US official said: “He was very clear that we have a short window of time to help the Ukrainians to prepare for an offensive and that they had some pretty specific needs.”

The Daily Telegraph, London