The Russian offensive in Donbas is at a standstill, according to the UK Ministry of Defence.
British intelligence experts say Russian forces lost strength and were significantly delayed.
They also estimate that the Russians lost about a third of the ground forces they committed to at the start of the invasion in February.
Analysts wrote: “Russia’s Donbass offensive has lost steam and has been significantly delayed.
“Despite initial small-scale advances, Russia has failed to make substantial territorial gains in the past month, maintaining consistently high levels of attrition.
“Russia has now likely suffered losses of a third of the ground combat force it committed in February.”
They added: “Russian forces are increasingly constrained by degraded enabled capabilities, continued low morale, and reduced combat effectiveness.
“Many of these capabilities cannot be replaced or reconstituted quickly and are likely to continue to hamper Russian operations in Ukraine.”