By Ashe O

Washington, Oct 13 (IANS): US President Joe Biden ruled out talks with his Russian counterpart Vladimir Putin at the upcoming G20 summit at Indonesia, saying "there is no rationale to meet with him now".

Asked during a CNN interview whether he would meet Putin at the summir, Biden said he didn't see a good reason for a sit-down.

"It would depend on specifically what he wanted to talk about," Bhe said, adding if Putin wanted to discuss the jailed American basketball star Brittney Griner, then he would be open to talking.

"He's acted brutally... I think he's committed war crimes. And so, I don't, I don't see any rationale to meet with him now."

Biden said threats arising from Russia's ongoing invasion of Ukraine is a "miscalculation "that could lead to catastrophic consequences close on the heels of his earlier warning that the world ran a risk of "nuclear Armageddon".

President Biden told CNN that "threats emanating from Russia could result in catastrophic "mistakes" and "miscalculation," even as he declined to spell out how precisely the US would respond if Putin deploys a tactical nuclear device on the battlefield in Ukraine.

When asked whether the Putin would use a tactical nuclear weapon, a prospect US officials have watched with concern as Russian troops suffer embarrassing losses on the battlefield, Biden said: "I don't think he will... I think it's irresponsible for him to talk about it, the idea that a world leader of one of the largest nuclear powers in the world says he may use a tactical nuclear weapon in Ukraine."

He said even Putin's threats have a destabilizing effect, and warned of the potential errors in judgment that could ensue.

"The whole point I was making was it could lead to just a horrible outcome," he told CNN. "And not because anybody intends to turn it into a world war or anything, but just once you use a nuclear weapon, the mistakes that can be made, the miscalculations, who knows what would happen."

Putin "in fact, cannot continue with impunity to talk about the use of a tactical nuclear weapon as if that's a rational thing to do", Biden said.

"The mistakes get made. And the miscalculation could occur, no one can be sure what would happen and could end in Armageddon."

The President refused to disclose what a US response would look like should Putin follow through on his nuclear threats. But he said the Department of Defence had proactively developed contingencies should the scenario come to pass.

Biden said he believed Putin is a "rational actor" who nonetheless badly misjudged his ability to invade Ukraine and suppress its people.

Biden, his top officials and fellow Western leaders have spent the past several months debating what steps Putin may take as his troops suffer embarrassing losses on the battlefield in Ukraine.

A counter-offensive launched by Ukraine last month was successful in retaking territory previously held by the Russians, including critical transportation hubs.

The losses proved the latest major embarrassment for Russia, whose military has struggled over the course of the seven-month war.

This week, however, Russia launched one of its fiercest bombing campaigns since the war began on February 24.

At least 19 people have been killed and more than 100 wounded across the country, as far away as the western city of Lviv, hundreds of miles from the war's main theatres in eastern and southern Ukraine.

Biden spoke to CNN a few hours after meeting virtually with members of the G7 industrialized nations, who heard from Ukrainian President Volodymyr Zelensky on the need to bolster his country's air defences amid the new Russian bombardments.

Zelensky told the meeting that "common efforts to create an air shield for Ukraine" must be intensified amid a barrage of Russian cruise missile and drone attacks.

White House officials have said the US is prepared to further bolster Ukraine's air defences, including through missile defence systems that Biden expedited delivery of over the summer.

Yet Russia's intense aerial assault of the Ukrainian capital Kiev and on civilian infrastructure suggested Putin could be employing new tactics meant to terrorise the country as winter approaches.