New nuclear threats raise risk from a 'cornered Putin': Experts

Even before Russian troops invaded Ukraine, U.S. officials warned global peace would be endangered if Russian President Vladimir Putin were allowed to brazenly seize another sovereign country.

At the same time, analysts have warned that if he faced no option but defeat in that bid, the outcome could prove to be even more dangerous -- a so-called "cornered Putin."

Ukrainian successes on the battlefield have not only pushed Russian troops back but now have pushed Putin further into a corner -- forcing him to take a series of dramatic steps to reinvigorate his brutal campaign: a sweeping military draft, labeled as a "partial mobilization," to surge thousands of soldiers to the fight, and orchestrating what the West has called "sham" referenda in occupied territories in Ukraine -- intended to pave the way for them to be "annexed" -- considered, in Putin's view, to be part of Russia.

Most alarming, in a rare televised address, Putin also issued a new round of thinly-veiled nuclear threats -- warning that Russia will use "all available means" to protect what he now portrays as Russian people and territory.

While some of his rhetoric isn't new, the changed circumstances in the conflict are. ABC News spoke to experts and former U.S. officials about why Putin's latest saber-rattling escalates risks -- for both Putin and the world.

Losing the home crowd

Putin's "partial mobilization" to send Russians who have gone through military training to serve in Ukraine is broadly seen as a tacit acknowledgement that his military is failing to accomplish Moscow's goals in Ukraine.

But Max Bergmann, a former State Department official and the director of the Europe Program at the Center for Strategic and International Studies, says it also puts Putin's control over his own country in question.

"What is clearly happening here is that the Russian military position in Ukraine is collapsing," he said. "Forcing people to go and fight in Ukraine is an extremely risky political decision. This is one of the most incredibly disruptive things that can be done to a society."

Although economic penalties for the invasion continue to have a mounting impact, Bergmann says the move will bring the war home to many Russians for the first time. And what's worse, he adds, is that Putin hasn't even officially called his invasion of Ukraine a war -- still describing it as a "special military operation."

"There's a total disconnect between the Russian government messaging that this is just some sort of tactical military effort in Ukraine, versus the need to suddenly rip men that have maybe at one time in their life served in the military for a year away from their families -- many with children -- and from their jobs, off to a battlefield where tens of thousands of people are dying," he said.

Despite the Kremlin's efforts to silence protest, Bergmann says if enough discontent builds, Putin risks losing public support, and with it, his grasp on power.

"He is gambling his entire regime over Ukraine," he said.

A powerful tool in Putin's arsenal is the state propaganda machine, but Bergmann believes Putin still has a steep hill to climb in portraying the war as defending the motherland.

"Putin hopes he can harken back to Russia's past of repelling invaders, whether it's Napoleon's army or Hitler's. But then, Russia was being invaded. It was an existential war. This is a war of imperial ambition," he said. "He's going to have to work incredibly hard to convince the Russian public that it's worth it to lose their husbands, fathers and sons in an oblast in Ukraine."

While the Russian president still appears to wield uncompromising control, Bergmann warns the tide can shift quickly.

"Autocratic regimes look incredibly stable until they're not," he said.

Buying time

Ukraine's President Volodymyr Zelensky, in his speech this week to the United Nations General Assembly, warned Moscow was trying to wait his fighters out.

"Russia wants to spend the winter on the occupied territory of Ukraine and prepare forces to attempt a new offensive," he said in a recorded address.

Analysts also say buying time to move newly conscripted troops to the front might be the motivator behind other elements of Putin's strategy.

"Those troops will take a while to get to the battlefield," said John Hardie, deputy director of the Foundation for Defense of Democracies' Russia Program. "It's definitely a game on his part."

Putin's latest efforts towards annexation, coupled with promises to defend its land, are likely aimed at giving Ukraine second thoughts about pursuing its counteroffensive -- and giving the West second thoughts about supporting it, Hardie and Bergmann said. But they say it's unlikely to prove effective.

"Putin's hope is that this causes Ukraine and the West to freak out to give some pause about further advances," Bergmann said. "But I think support for Ukraine will remain strong. And that Ukraine is going to advance militarily as it sees fit."

One senior administration official called the referenda a "crass and desperate" maneuver that would not alter the U.S. outlook on the conflict, and predicted that other powers around the world -- even those more closely aligned with Russia -- would not be significantly swayed.

Still farther to fall

If Putin's attempts to delay Ukraine's military progress fail, the most pressing question becomes whether he will make good on his threats to go nuclear -- and what the U.S. and its allies might do in response.

"It's something that you have to take very seriously. Russia has the world's largest nuclear arsenal," said Bergmann. "And when the Russian president starts making nuclear threats, it's something everyone has to pay attention to."

While both Hardie and Bergmann agree Putin doesn't appear ready to resort to the nuclear option, they say deterrence must be the priority. American officials have publicly and privately warned Moscow against using nuclear weapons, and Hardie said they should also press countries the Kremlin might be more receptive to listening to -- such as China and India -- to send the same messages.

But the consequences Russia could expect to face are less clear.

"Are we actually ready to do something more than sanctions? I tend to think we are probably not. I think the administration rightly wants to avoid World War III," said Hardie.

Because of this, the Biden administration's "strategic ambiguity" on repercussions is the best available avenue, he argues.

"If offers the benefit of leaving doubt in Putin's mind," Hardie said.

While Putin could ultimately disregard any doubts, Hardie says it will likely require Putin to grow considerably more desperate.

"I think this would be very much a last resort," he said, noting the Kremlin might test the waters first with demonstrations before hitting critical infrastructure or troop concentrations. "But I think we're a long way from that point."

But Hardie said a significant incursion into Crimea -- the peninsula annexed by Russia from Ukraine in 2014 -- would likely move the needle much more, and that it's possible Putin will decide to protect any newly annexed territory with the same ferocity.

"We're in uncharted waters," he said.