Top news: Russia's war effort in Ukraine is 'running out' as Putin's ability to spy on Europe halved, says MI6 chief

The head of Britain's foreign intelligence service believes Russia is losing steam in its invasion of Ukraine and has lost "half" of its ability to spy on Europe after more than 400 Russian intelligence officers were expelled from cities across Europe and arrested several undercover spies posing as civilians.

Richard Moore, the head of MI6, told at the Aspen Security Forum that since Russia invaded Ukraine in February, European countries have expelled "north of 400 Russian intelligence officers operating under diplomatic cover" from across the bloc.

"And we reckon that in the UK it's probably halved their ability to do their spying for Russia in Europe," Moore said. He added that a number of "illegals," or Russian spies operating under deep cover and posing as ordinary civilians, had also been uncovered and arrested in recent months.

Moore also said he believed Russia could be "running out of breath" in Ukraine.

"I think our assessment is that it's going to be increasingly difficult for the Russians to deliver manpower material over the next few weeks," he said. "They will have to stop somehow, and that will give the Ukrainians an opportunity to strike back."

"Their morale is still high," Moore said, referring to the Ukrainians. They're starting to get more and more good guns. Russia, on the other hand, has failed significantly in its original goals of capturing Kyiv and overthrowing the government there, and is largely using "cannon fodder" for its offensives in eastern Ukraine, he said.

Asked whether the war in Ukraine had made Russia a "target-rich environment" for Britain and its allies to recruit potential assets, Moore said only that "it is our hope" that the Russians in the intelligence and diplomatic services are "thinking about what they are witnessing in Ukraine" and will decide to "strike again against the system" as many did during the Prague Spring in 1968. "Our door is always open," he said.

Moore also echoed what CIA Director Bill Burns said Wednesday at a forum about Russian President Vladimir Putin's health. "There is no evidence that Putin suffers from a serious disability," he said. Burns told the forum that the US believes Putin is "far too healthy", despite rumors and speculation that he may be ill.

Asked what lessons China had learned from Russia's invasion of Ukraine, particularly whether Beijing might try to invade Taiwan, Moore said it was too early to tell. But he said Chinese President Xi Jinping was watching the conflict and how the US and the West were reacting to it "like a hawk".

"I think he underestimates the resolve and the power of the US," Moore said.  And that could lead him to miscalculate… especially regarding Taiwan. However, Moore said he does not believe a war between China and Taiwan is inevitable.

Moore said MI6 now devotes "more effort to China than any other single entity" but that it is "still quite an opaque system".

"On one level, understanding Xi's strategic intent is not difficult," Moore said, referring to Xi's stated desire to dominate key technology spaces. "But if you go underneath that strategy, in terms of how they implement, how they organize, how they, what their tactical intent is and what the capabilities they're building, it's a black box."

Moore said it was clear, however, that the Chinese were "helping the Russians with Ukraine by buying their oil." And while they were "quite conservative in terms of military aid" to Russia, "I'm sure if they could give it and get away with it, they would," he said. As for the partnership between the countries, "Moscow is very much the junior partner and the Chinese are very much in the driver's seat," he added.

Moore also weighed in on the Iran nuclear deal, telling Sciutto that while he believes the deal should be renewed, '' I'm skeptical that the supreme leader will go along with the deal. I think a deal is absolutely on the table, and the European powers and the administration are very, very clear about that. And I don't think the Chinese and Russians would block it on this issue. But I don't think the Iranians want that.''