Russia is "about to run out of steam" in Ukraine, giving Kyiv's military a chance to strike back, said the head of Britain's foreign intelligence agency, or MI6.
Speaking at the Aspen Security Forum on Thursday, Richard Moore said Russian troops would face supply and logistics problems in the coming weeks.
"The Russians will increasingly find it difficult to supply manpower and material over the next few weeks," he said. "They will have to pause in some way and that will give the Ukrainians opportunities to strike back."
Noting that Russia only made "a small number of miles of advance" in the recent weeks, he said: "When they take a town, there's nothing left of it ... it is obliterated, and so I think they're about to run out of steam."
Asked about speculation that Russian President Vladimir Putin was unwell, the intelligence chief said that "there’s no evidence" he has serious health issues.
Over 5,100 civilians have been killed in Ukraine since the beginning of the war on Feb. 24, according to UN figures. Over 15 million people have also been forced to flee their homes, including more than 9.5 million that have fled to other countries.