Russia's Vladimir Putin's luck might have run out, but he remains willing to sacrifice 20 million of his soldiers to cling to objections in Ukraine, a former Russian diplomat says.

"You should have no doubt about it, he may sacrifice 10 or 20 million Russians just to win this war just to slaughter all Ukrainians because it's a matter of principle," Boris Bondarev, who quit in May as a nuclear disarmament ambassador to the United Nations in Geneva over Putin's war, told Sky News. "It's a matter of political survival to him.

"You have to understand that, if he loses the war, it will be the end for him."

Putin is using nuclear blackmail to "compel other countries to whatever he wants," added Bondarev, who is calling for a regime change in Russia — stoking the flames of desperation of a leader clinging to power.

"I think the 20 years of him in power have been very lucky for him," he continued. "He is not smart, he is just lucky. Now I think his luck is over."

Bondarev vowed to quit the day the Russian tanks crossed into Ukraine in February, saying he could "no longer work for this government, this country," but he held out until May, so he could save his cat as Russia was "making war crimes and terrible mistakes and crimes against our future generations."

"I had some affairs to be settled before I quit," he said. "My cat was in Moscow at the time, so we had to get him back to Geneva and it took three months.

"During these two months I was very afraid.

"After the war started, they all turned out to be warmongering and very content with what is going on."

Bondarev "did not believe President Putin was seriously going to start the war," but now he is convinced the Russian dictator is desperate to sacrifice lives to save face.

"After losing the war, he will have to explain to his elites and his population why it is so and he may find some problems in explaining this," Bondarev said.

"And after that there may be opposition who will try to depose him or he will try to purge his subordinates to find some people who could be blamed for all these problems. There will be a period of internal turmoil."

But first, there will be nuclear escalation in a "new level of history of nuclear weapons," he warned, calling it a "very dangerous development."

"I believe that there can be some plans to somehow deploy nuclear weapons during this war in Ukraine," he said.

"The West, I think, must be consistent to remove Putin because while he and his regime is still in power in Russia, the threat of nuclear war will not go anywhere."

While NATO expansion was the primary reason for Putin starting the war, Bondarev believes NATO should consider entering the conflict between Ukraine and Russia.

"Putin thinks he's already waging the Third World War," Bondarev said.

Short of direct military protection, Bondarev added calls for weapons armament for Ukraine.

"They need offensive weapons, more long-range missiles, aircraft," he said. "So I think NATO must double down the efforts and help.

"Russian people, especially younger generations, they don't see NATO as some kind of existential enemy, they are totally OK with that, as NATO is a defensive organization."

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