Ukrainian President Volodymyr Zelenskyy said Russian forces are suffering heavy losses and the notion that Moscow is winning the nearly two-year-old war is only a "feeling" not based on reality.
"Thousands, thousands of killed Russian soldiers, nobody even took them away," he told The Economist magazine in an interview published on Monday, referring to fighting around the besieged eastern town of Avdiivka which he visited last week.
He provided no evidence to back up his assertion but Western military analysts agree Russia is paying a heavy price in men and equipment for relatively minor gains in eastern and southern Ukraine.
There was no response to a request for comment from Russian officials on Zelenskyy's remarks.
Russian officials have said Western estimates of Russian death tolls are vastly exaggerated and almost always underestimate Ukrainian losses.
Russian President Vladimir Putin said last month Russia's position was improving and it would not stop what he calls the "special military operation" until its objectives, including Ukraine's "denazification, demilitarisation and its neutral status", have been achieved.
Russian officials have dismissed as a failure a Ukrainian counteroffensive launched in mid-2023 in the east and south.
Zelenskyy acknowledged that the counteroffensive backed by advanced Western weapons may not have succeeded "as the world wanted. Maybe not everything is as fast as someone imagined."
In contrast, he hailed the "huge result" of Ukrainian forces breaking through a Russian Black Sea blockade, enabling grain exports by way of a new route along its southern coast.
If Ukraine lost the war, he said, Russia would be encouraged to advance against other countries because "Putin feels weakness like an animal, because he is an animal. He senses blood, he senses his strength."
Mobilising Ukraine and the world
With support for Ukraine facing obstacles in the United States and European Union, more needed to be done to persuade the world that defending Ukraine meant defending the world, Zelenskyy said.
"Maybe something is missing. Or maybe someone is missing," he told the magazine. "Someone who can talk about Ukraine as a defence of all of us."
Zelenskyy acknowledged that "mobilisation of Ukrainian society and of the world" that was so strong at the start of Russia's invasion is not there anymore.
Ukraine saw tens of thousands of men volunteer to fight in the first months of Russia's invasion, but that enthusiasm has waned 22 months later.
"That needs to change," he said. "Mobilisation is not just a matter of soldiers going to the front. It is about all of us. It is the mobilisation of all efforts. This is the only way to protect our state and de-occupy our land."
Zelenskyy has embarked on a flurry of international trips trying to shore up Western support. At home, he has repeatedly urged Ukrainians to do their duty.
"Victory is not received or granted, it is gained,"Zelenskyy said in his New Year message to Ukrainians. "And to this end, today we have to live by the rule: you either work or you fight."
A draft law that proposed lowering the mobilisation age to 25 from 27 has sparked controversy.
Russia has said it is ready for peace talks if Ukraine takes account of "new realities", suggesting an acknowledgement that Russia controls about 17.5 percent of Ukrainian territory.
Zelenskyy rejected any notion that Moscow was interested in talks, pointing to its repeated waves of aerial strikes. Russia would only agree to a pause in fighting if it needed a break to replenish its army, he said.