Moscow’s hopes of storming Kiyv in a matter of days were dashed when its armed forces encountered fierce resistance from Ukrainian forces. The Kremlin quickly changed strategy in an attempt to gradually encircle key cities and strangle resistance forces within them.

However, as the conflict enters its fourth week, Western officials say the Kremlin’s backup plan is failing to make a significant difference.

“Not only is it not going as planned, but even as they have adjusted to a more grinding form of warfare, that is stalling,” one official said.

“There is a lot of encouraging resistance from Ukrainians.”

Another added: “We’re continuing to see that Russian forces are continuing to make little bits of progress here and there but they’re not achieving any strategic breakthrough at any point.

“Their ground forces are still heavily reliant on Ukraine’s road network, which obviously limits them to some extent.

“Their off-road manoeuvrability is fairly limited, which means that Ukrainians have been able to destroy some infrastructure, such as bridges, as well as ambush Russian columns.

“All of this means that Russia’s progress has been significantly slowed.”

So far, it is estimated that up to 7,000 Russian troops have died in the invasion.

Putin and Kremlin officials are believed to have grossly underestimated the level of opposition they would face in Ukraine, leaving them unprepared for urban combat.

Ukraine’s defence has been bolstered in part by military supplies provided by other countries.