U.S President Joe Biden said Tuesday he believes his Russian counterpart Vladimir Putin is a normally rational actor who badly misjudged his prospects of occupying Ukraine.

The president spoke out in a rare televised interview as his administration looks for what he has described as an "off-ramp" for Putin to deescalate his invasion of Ukraine before he resorts to weapons of mass destruction.

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

Biden warned last week that the world risks "Armageddon" in unusually direct remarks about the dangers from Putin's thinly veiled threats to use nuclear weapons to assist Russia's faltering attempt to take over swaths 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 while he believed Putin was rational, he 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.

The president even left open the possibility of talks with his Russian counterpart on the sidelines of the meeting of G-20 nations in Bali scheduled for November – although he was clear there are no plans for talks on Ukraine.

"Look, I have no intention of meeting with him," Biden told CNN, adding that he would however see Putin if the Russian leader wanted negotiations over releasing detained US basketball star Brittney Griner.

"If he came to me at the G-20 and said 'I want to talk about the release of Griner,' I'd meet with him. I mean, it would depend," he said.

Further escalation

Kyiv's forces have in recent weeks been pushing back against Russian soldiers across the front lines in the south and in the east.

Ukrainian President Volodymyr Zelenskyy said Friday his troops had recaptured nearly 2,500 square kilometers (965 square miles) in the counter-offensive that began late last month.

But the Ukrainian Defense Ministry said Monday that Russia had retaliated with a massive bombardment of its neighbor, 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 industrialized 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 G-7 "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 defenses to Ukraine, while Germany promised delivery "in the coming days" of the first Iris-T missile shield reportedly capable of protecting a city.

No neutrality

Meanwhile, the United States was leading an all-out offensive to rally as many countries as possible to adopt a resolution at the U.N. 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 spokesperson Ned Price.

U.N. 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-on-one televised interviews.