"Vladimir Putin must not be allowed to win this war in Ukraine. More than that, he must not be allowed to have a face-saving exit from this war," Russian opposition figure Vladimir Kara-Murza said at a press conference in London.

A recent poll found that 49 percent of people would back withdrawing without achieving the Kremlin's military objectives.

Vladimir Putin cannot win the war in Ukraine because his defeat is the only chance to build a new, democratic Russia. The Russian opposition and the West cannot waste this opportunity again as they did in the '90s,