Speaking at a security forum in Aspen (USA), Moore said that Russia will soon face problems in supplying its troops in Ukraine.

"In the next few weeks, it will be increasingly difficult for the Russians to supply troops and materials.

They will have to make a pause, and this will give the opportunity to the Ukrainians to strike back," Moore was quoted by the British edition of the Financial Times.

According to the head of MI6, Russia's recent successes in the military campaign have been very limited.

He emphasized that it is very important for Ukraine to demonstrate its ability to retaliate against Russian troops.

"It will be an important reminder to the rest of Europe that the Ukrainians can win this campaign, because we're going to have a pretty tough winter," he said.

"I don't want to sound like a Game of Thrones character, but winter is coming and it's clear that in this environment, with this pressure on gas suppliers and everything else, we're going to have a tough time."

Moore also called for active Western support for Ukraine, explaining that in the broader geopolitical context, this would affect China's intentions.

"One of the reasons why it's so important that we stand firm on Ukraine ... and that we help the Ukrainians win or at least negotiate from a position of significant strength is that Xi Jinping is watching this like a hawk," Moore said.

The head of British intelligence is worried that because China's leader has a "very entrenched narrative" about the West's weakness, Russia's war in Ukraine could cause Xi Jinping to underestimate US power and lead to rash actions on Taiwan.