Cold winters helped Moscow defeat Napoleon and Hitler. President Vladimir Putin is now betting that sky-rocketing energy prices and possible shortages this winter will persuade Europe to strong arm Ukraine into a truce -- on Russia's terms.

That, say two Russian sources familiar with Kremlin thinking, is the only path to peace that Moscow sees, given Kyiv says it will not negotiate until Russia leaves all of Ukraine.

"We have time, we can wait," said one source close to the Russian authorities, who declined to be named because they are not authorised to speak to the media.

"It's going to be a difficult winter for Europeans. We could see protests, unrest. Some European leaders might think twice about continuing to support Ukraine and think it's time for a deal."