The US intelligence community believes that Russian President Vladimir Putin views the conflict in Ukraine as a "war he cannot afford to lose," suggesting he is likely to escalate the conflict without any concern for the number of civilians killed, the US's top intelligence chiefs told Congress, CNN reported.

Director of National Intelligence Avril Haines said at a congressional hearing Tuesday that US intelligence assesses Putin is unlikely to be deterred by the setbacks the Russian military has faced in Ukraine, suggesting he is doubling down on his campaign to keep Ukraine from joining NATO.

Putin's announcement last week that he was elevating the readiness status of his nuclear forces was "very unusual," Haines told lawmakers on Tuesday. But she said that it was better understood as messaging rather than an immediate threat to the United States.

"We obviously take it very seriously when he's signaling in this way," Haines said. "But we do think [that] he is effectively signaling, that he's attempting to deter" NATO from getting involved in the conflict in Ukraine, she said.

"That's been his main purpose in doing so," Haines added.

Haines also said that the Russian announcement that the country's strategic forces would be placed on "special alert status" did not refer to a "technical term as we understand it within their system"

Haines said that US intelligence believes Putin's "nuclear saber-rattling" and public posturing are part of an effort to deter the US and NATO from engaging in the war and from providing additional support to Ukraine.

"Putin probably still remains confident that Russia can militarily defeat Ukraine and wants to prevent Western support from tipping the balance and forcing a conflict with NATO," Haines said.

She said Russia had initially underestimated the strength of Ukraine's resistance, adding that Moscow's ultimate military objectives remain unclear.

"What is unclear at this stage is whether Russia will continue to pursue a maximalist plan to capture all or most of Ukraine, which we assess would require more resources even as the Russian military has begun to loosen its rules of engagements to achieve their military objectives," Haines said.

The Russian military, she said, is operating "with reckless disregard for the safety of noncombatants as Russian units launch artillery and airstrikes into urban areas."

CIA Director William Burns said Putin had launched the invasion "determined to dominate and control Ukraine" based on a set of assumptions that the conflict would be successful, including that Ukraine was weak, that European allies like France and Germany were risk-averse, that he had "sanctions-proofed" his economy and that his military was capable of a quick and decisive victory at minimal cost.

CIA Director William Burns said Putin had launched the invasion "determined to dominate and control Ukraine" based on a set of assumptions that the conflict would be successful, including that Ukraine was weak, that European allies like France and Germany were risk-averse, that he had "sanctions-proofed" his economy and that his military was capable of a quick and decisive victory at minimal cost.

"He's been proven wrong on every count," Burns said.

"This is a matter of deep personal conviction for him," Burns told the committee. "He's been stewing in a combustible combination of grievance and ambition for many years."

Burns predicted an "ugly next few weeks" with "scant regard for civilian casualties," given Moscow is unlikely to be able to install a puppet regime or pro-Russian leadership in the face of opposition from the Ukrainian people.

"The Ukrainians are going to continue to resist fiercely and effectively," he added.