Boris Johnson has told Sky News that he does not think Vladimir Putin will use a tactical nuclear weapon in his war in Ukraine.

There have been suggestions that the Russian president could carry out such a military strike as his forces continue to lose territory which they captured earlier in the invasion.

But in an exclusive interview for Sky News’ Ukraine: A Modern War programme, the ex-prime minister told Sky’s Mark Austin: “I don’t think he will, he’d be crazy to do so.”

Mr Johnson also said he will be travelling to the COP27 climate summit in Egypt next week, as question marks remain over whether Rishi Sunak will join him.

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Mr Johnson said using a nuclear weapon would mean Mr Putin “would immediately tender Russia’s resignation from the club of civilised nations”.

The former UK leader said it would be a “total disaster” for Russia, which would be put into a “cryogenic economic freeze” and Mr Putin would “lose a lot of the middle ground of global tacit acquiescence that he’s had”.

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Johnson’s close relationship with Zelenskyy still holds sway

Deborah Haynes

Security and Defence Editor

@haynesdeborah

He may be a former British prime minister, but any comment made by Boris Johnson on the war in Ukraine still carries weight, especially when it comes to nuclear weapons.

His uniquely close relationship with Ukrainian President Volodymyr Zelenskyy and his decision to be a leading voice amongst Western allies in supporting Ukraine from the outset of the invasion has made London one of Kyiv’s most trusted and valued partners.

It also gave Mr Johnson privileged access during his time in office to the private thoughts of Mr Zelenskyy as well as a deep understanding of Ukraine’s need to defeat Russia’s invasion and the threats it could face – all the way up to Vladimir Putin launching a nuclear strike.

Read the full analysis here

Mentioning sub-Saharan Africa, Latin America, and South Asia, Mr Johnson said: “There’s a lot of willingness to give Putin the benefit of the doubt. That will go, the minute he does anything like that.

“He would also crucially lose the patronage of the Chinese. And in his own country, I think he would trigger an absolutely hysterical reaction.”

You can watch the full interview on Ukraine: A Modern War on Sky News from 7.30pm tonight

Mr Johnson said if there was such a military act from Mr Putin, there would have to be a response of some kind.

“There are all sorts of options” both in NATO and the P3 nations (US, UK and France), he said.

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3:22

What is a tactical nuclear weapon?

But he added he thought it was “very, very, very, very unlikely that it will come to that (a tactical nuclear attack by Putin)”.

He also said it was a “critical” and “pivotal moment” for the world.

Looking ahead to how the conflict could be resolved, the former PM warned about the danger of trying “to comprise and find some sort of deal, some grubby bargain with Putin”, trying to encourage the Ukrainians to trade some of their territory, which Mr Johnson said “will only encourage Putin to make further aggression”.

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1:52

Putin’s only aim is to ‘spread terror’

He said that it is going to be very difficult for the Ukrainians to accept any deal that stops short of a full return of all the areas taken by Russia since the invasion began on 24 February.

Mr Johnson also said it was “absolutely inevitable” that the Ukrainians will eventually win the war.

“We have to show strategic patience and continue to support them,” he added.