An official in Vladimir Putin’s inner circle has warned the West that Ukraine joining Nato would mean “a guaranteed escalation” to a third world war.

Alexander Venediktov, the deputy secretary of Russia’s Security Council, told the state-run TASS news agency that the superpower wouldn’t back down if the nation under siege was offered an official spot among Western powers.

His warning came days after Putin promised to continue targeting civilian locations following Ukraine’s destruction of a crucial supply bridge in Crimea.

Earlier this month, Ukraine President Volodymyr Zelensky announced his nation is submitting an “accelerated” application to join the Nato military alliance, following Russia’s annexing of four territories in the country’s east.

Flame and smoke rise fron Crimean Bridge connecting Russian mainland and Crimean peninsula over the Kerch Strait, in Kerch, Crimea. Photo / AP

“Kyiv is well aware that such a step would mean a guaranteed escalation to a world war three,” Venediktov said.

“Apparently, that’s what they are counting on – to create informational noise and draw attention to themselves once again.”

Venediktov said Western nations continuing to supply Ukraine with aid and military equipment “are a direct party to the conflict”.

Ukraine’s Nato allies this week announced deliveries of advanced air defence weapons to Kyiv, following a plea from Zelensky in the days after the capital was struck by a horrific missile strike — the first of its kind since June.

• Iranian-made kamikaze drones strike near Kyiv
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Biden said Tuesday he believes his Russian counterpart badly misjudged his prospects of occupying Ukraine.

“I think he is a rational actor who has miscalculated significantly,” Biden told CNN after Moscow’s shelling of civilian targets across its neighbour marked an escalation in the seven-month conflict.

Biden warned last week that the world risks “armageddon” in unusually direct remarks about Putin’s thinly veiled threats to use nuclear weapons in Russia’s faltering attempt to take over swathes of Ukraine.

Putin’s state of mind has been the subject of much debate after the Russian President suffered a series of recent military setbacks in the invasion, which he launched in February.

Biden told CNN that he believed Putin had underestimated the ferocity of Ukrainian defiance.

“I think … he thought he was going to be welcomed with open arms, that this was the home of Mother Russia in Kyiv, and that where he was going to be welcomed, and I think he just totally miscalculated,” Biden said.

However, Western support for the Ukraine war has brought about several high-profile detractors, who believe the most peaceful way to end the conflict is to promote UN-sanctioned referendums for the regions currently under Russian control.

Former US Congresswoman Tulsi Gabbard this week described the Ukraine conflict as a “proxy war”, accusing the US of “using Ukraine as our military” to achieve its goals against Putin.

Abandoned Russian tanks stand on the road in recently liberated town Kupiansk, Ukraine on October 1. Photo / AP

Gabbard claimed global escalation was “just a flick of a match away” and urged leaders to stop “fuelling” the war and push for a negotiated outcome.

“You hear President Biden say ‘this is Putin’s war, this is Putin’s fault, it is Putin who is the one solely responsible’,” she said.

“The United States and some of these European Nato countries are fuelling this war and need to provide the leadership to bring about a negotiated outcome. That is what needs to happen here to prevent the destruction of the planet and life as we know it.

“They’re not doing that and they are failing the American people and putting us in this position of not knowing where we’re going to be in the event this kicks off.”

Biden has left open the possibility of talks with his Russian counterpart on the sidelines of the meeting of G20 nations in Bali scheduled for November - although he was clear there are no plans for talks on Ukraine.

Despite devastating scenes raining down on its capital cities, Ukraine’s forces have in recent weeks been pushing back against Russian soldiers across the front lines in the south and in the east.

Zelenskyy said Friday his troops had recaptured nearly 2500 sq km in the counteroffensive that began late last month.

But the Ukrainian defence ministry said Monday that Russia had retaliated with a massive bombardment of its neighbour, hitting the Ukrainian capital Kyiv for the first time in months, as well as other cities across the country.

Biden spoke to CNN hours after meeting virtually with members of the Group of 7 industrialised nations, who heard from Zelenskyy on the need for intensified efforts to “create an air shield for Ukraine” amid the barrage of Russian cruise missile and drone attacks.

Zelenskyy told the G7 that “millions of people would be grateful” for help fending off attacks from the sky, and he warned Russia “still has room for further escalation”. Washington pledged after Monday’s bloody salvos that it would up shipments of air defences to Ukraine, while Germany promised delivery “in the coming days” of the first Iris-T missile shield reportedly capable of protecting a city.

Meanwhile, the United States was leading an all-out offensive to rally as many countries as possible to adopt a resolution at the UN condemning Moscow’s annexation of Ukrainian regions.

“We believe the time has long passed for neutrality. There is no such thing as neutrality in a situation like this,” said State Department spokesman Ned Price.

UN countries are debating a resolution introduced to the General Assembly by Ukraine, which the West hopes will demonstrate the isolation of Putin’s Russia on the international stage, with a vote likely on Wednesday or Thursday.

Biden frequently takes questions from the media, but he has held few press conferences or one-to-one televised interviews.