Vladimir Putin "on one level" has "already lost", Defence Secretary Ben Wallace has said while talking about the war in Ukraine.
His words came as Russia claimed victory in the strategic south-eastern city of Mariupol, however, Mr Wallace said Ukrainian forces had pushed back "a number of advances" in the east.
The UK Ministry of Defence has reported that the Russian president probably wants to demonstrate significant successes ahead of his country's annual Victory Day on 9 May.
But Mr Wallace said he was "not sure" what Mr Putin would be celebrating "other than being isolated".
The Defence Secretary told Forces News that the Russian president "has built himself a cage and put himself in it".
"I think Russia's already lost. Russia's ambition was to occupy Ukraine and invade it and surround or take Kyiv - well, that hasn't happened," he said during a visit to the Invictus Games in The Hague.
"Russia have had horrendous casualty rates because of the incompetence of their generals and poor leadership.
"Their equipment has shown to be not very good, their leadership and their doctrine has failed... so on one level, Putin has already lost."
Mr Wallace also called Mr Putin a "pariah" whose nation is "lesser than it was at the beginning of this campaign".
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The former Army officer said Russia's invasion is having an "opposite" effect, encouraging more nations such as Finland and Sweden to consider joining NATO.
Western nations are continuing to send military hardware to Ukraine.
Mr Wallace said he will make a statement to Parliament in the next week about the UK sending additional equipment.
The Defence Secretary declined to confirm to the PA news agency whether Stormer armoured anti-aircraft vehicles have been sent to Ukraine, but said the UK will "continue to give them the air defence they need".
He told Forces News: "He [Putin] is stretching his armed forces.
"They are being worn out.
"You don't take casualties like he is taking and recover quickly.
"At the end of this, whatever happens, Putin is going to end up with an army that is exhausted, worn out, with a very poor reputation for Russian equipment.
"I mean who is going to be buying some of their kit now? I think there's a lot of problems for the Russian army to come."