Ukrainian President Volodymyr Zelensky has said the notion that Russia is winning the nearly two-year-old war is only a "feeling" and that Moscow is still suffering heavy battlefield losses.
Interviewed by The Economist, he provided no substantiation of his claim on Russian losses.
President Zelensky said that Ukraine's priorities in 2024 included hitting Russia's strengths in Crimea to reduce the number of attacks on his country as well as protecting key cities on the eastern front.
Russian President Vladimir Putin said last month that its position was improving on the front lines and it would not halt the campaign 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.
There was no immediate response to a request for comment from Russian officials on Mr Zelensky's latest remarks.
In his comments, he acknowledged: "Maybe we did not succeed (in 2023) as the world wanted. Maybe not everything is as fast as someone imagined."
However, he said the idea that Russian forces were winning was a mere "feeling," citing heavy Russian losses in the besieged eastern town of Avdiivka, which he visited last week.
"Thousands, thousands of killed Russian soldiers, nobody even took them away," President Zelensky said.
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."
With additional support for Ukraine facing obstacles in the United States and European Union, more efforts are needed to persuade the world that defending Ukraine meant defending the world, Mr Zelensky said.
"Maybe something is missing. Or maybe someone is missing. Someone who can talk about Ukraine as a defence of all of us."
Russia has said it is ready for peace talks if Ukraine takes account of "new realities", suggesting an acknowledgement that Moscow controls about 17.5% of Ukrainian territory.
President Zelensky rejected any notion that Russia was interested in talks, pointing to its repeated waves of aerial strikes.
"I see only the steps of a terrorist country," he said.
Any Russian call for talks "is not because they are righteous men, but because they don't have enough missiles, ammunition, or prepared troops. They need this pause. Restore all their strength. And then with all their strength, turn the page of this war."
Putin says Russia will 'intensify' attacks on Ukraine
Earlier, President Putin said that Moscow would intensify strikes on military targets in Ukraine after an unprecedented attack over the weekend on the Russian city of Belgorod.
It killed 24 people and left over 100 wounded and came after Moscow launched a large-scale attack on Ukrainian cities.
"We're going to intensify the strikes, no crime against civilians will rest unpunished, that's for certain," Mr Putin said during a visit to a military hospital.
Russia will press on with hitting what he called "military installations".
"We are doing that today, and tomorrow we will continue doing it," Mr Putin said, almost two years into Moscow's offensive.
He spoke as Ukraine said Russia had hit it with a "record" number of drones on New Year's Day.
Mr Putin called the Belgorod strike a "terrorist attack" and accused Ukrainian forces of targeting "right in the city centre, where people were walking, before New Year's Eve."
He repeated a claim that Ukraine is being used by the West to "settle its problems" with Russia.
The Russian leader said he believed the "strategic initiative" in the dragging conflict was on the Russian side.
"In any case that is how I am being briefed and I always insist: any offensive operations should be done after a defeat of the enemy," he said, according to the Interfax news agency.
