Russia has said it was delusional to think Ukraine could win the war, while Moscow's army said it had captured three more villages on the sprawling front line.
Both sides are heavily entrenched, almost four years after Russia launched its all-out invasion of Ukraine.
"The Europeans believe that Ukraine can win the war and secure its interests through military means," Kremlin spokesperson Dmitry Peskov said on Monday.
"This is the deepest delusion indulged in by the Kiev regime. The situation on the front indicates the opposite," he said in a briefing call with reporters.
The Russian defence ministry said on Monday it had seized the villages of Slodkie and Nove in the Zaporizhzhia region of Ukraine and Gnativka in the Donetsk region.
Peskov said the war would only end "when Russia achieves the objectives it set at the beginning".
Moscow has said it is fighting to protect Russian speakers in the east of Ukraine, to prevent the NATO military bloc moving eastwards and to remove "neo-Nazis" from power in Ukraine, all of which have been rejected as baseless by Kiev and its Western partners.
They say the conflict, which has resulted in the deaths of tens of thousands of people and has spiralled into Europe's largest since World War II, is nothing more than an imperial-style land grab.
Efforts by US President Donald Trump to force a peace deal have stalled.
Moscow has rejected calls to agree to a ceasefire and drop its demands.
Russian officials have said they will only discuss halting the offensive if Ukraine completely pulls out of the eastern Donbas region and renounces Western military support.
Kiev says those demands are non-starters, would be tantamount to capitulation and would leave it exposed to a further Russian attack.
Peskov said Russia had the initiative on the front and would not stop.
