Russia can afford to wage a long war in Ukraine despite being hammered by Western sanctions aimed at crippling its ability to sustain the campaign, defence experts and economists say.

Russia's invasion has driven up the price of the oil, gas, and grain it exports, providing it with a substantial windfall to fund its "special military operation" - now entering a new phase as Moscow focuses on the eastern Donbas region after failing to break Ukraine's defence of the capital Kyiv.

As the war grinds on, rising casualties and the need to rotate fresh troops into battle may...