Vladimir Putin’s assault on the Donbas region of eastern Ukraine could last for “several months”, a senior national security official has warned Boris Johnson and his cabinet.

       The prime minister told the regular weekly cabinet meeting at Downing Street that Ukraine’s position was “perilous”, as the Russian president was thought to want to be able to declare a victory of some sort “regardless of the human cost”.

       Following reports that Mr Johnson has promised Stormer mobile missile launchers to Ukraine’s president Volodymyr Zelensky, defence secretary Ben Wallace confirmed that he will announce new UK military aid later this week.

       The 13-ton armoured vehicles could be used to fire Starstreak missiles at Russian jets and helicopters.

       Mr Johnson was taking part on Tuesday afternoon in an international conference call with US president Joe Biden and leaders of France, Germany, Italy, Japan, Canada, Poland, Romania and the EU to discuss further assistance to the Kyiv administration on its 55th day of resistance to the Russian invasion.

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       The PM told cabinet it was “more vital than ever to increase global support” for Ukraine, and said he would use the call to push for addiational support and further toughening of sanctions.

       Mr Johnson told cabinet that “Ukraine's position remains perilous, with Putin angered by defeats, but determined to claim some sort of victory regardless of the human cost”, said the PM’s official spokesperson.

       The meeting was briefed by a senior national security official, who confirmed Putin was focusing his attention on the Donbas region, hwere pro-Russian separatists have been fighting official Ukrainian forces since 2014.

       The official said the next phase of the war was likely to be “an attritional conflict, which could last several months”.

       Russia would aim to exploit its troop numbers advantage but Ukraine had already shown that this was unlikely to be decisive on its own, cabinet was told.

       The official reported “some signs that Russia had not learned lessons from previous setbacks in northern Ukraine, and evidence of troops being committed to the fight in a piecemeal fashion”.

       There were continued reports of poor Russian morale, with claims of some soldiers and even units refusing to fight, the official said.

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       Chief of defence stuff Admiral Sir Tony Radakin told cabinet that the UK continues to play “a leading role” in military support to Ukraine, including in sourcing suitable equipment from other countries as other countries.

       Foreign secretary Liz Truss told the meeting the UK would continue to push for further coordinated action on sanctions and for other countries to allow Ukraine access to tariff free trade.