• The warning from the nation's top spymasters comes as Russia intensifies its now year-long fight in Ukraine and as Putin threatens to withdraw from a key nuclear arms treaty.
• Putin, whose country boasts the largest arsenal of nuclear weapons, has previously rattled the nuclear saber on the heels of Ukrainian advances on the battlefield.

WASHINGTON – Russian President Vladimir Putin is likely to further upgrade the Kremlin's arsenal of long-range nuclear-capable missiles in order to deter Kyiv and its powerful Western allies, U.S. officials warned Wednesday.

The warning from the nation's top spymasters comes as Russia intensifies its now year-long fight in Ukraine and as Putin threatens to withdraw from a key nuclear arms treaty.

"Throughout its invasion of Ukraine, Moscow has continued to show that it views its nuclear capabilities as necessary for maintaining deterrence and achieving its goals in a potential conflict against the U.S. and NATO and it sees its nuclear weapons arsenal as the ultimate guarantor of the Russian Federation," the nation's top intelligence agency wrote in its annual threat report.

The unclassified 35-page intelligence assessment adds that Moscow will become more dependent on nuclear weapons following significant battlefield losses and punishing rounds of sanctions that have crippled the Kremlin's ability to finance its war machine.

"Heavy losses to its ground forces and the large-scale expenditures of precision-guided munitions during the conflict have degraded Moscow's ground and air-based conventional capabilities and increased its reliance on nuclear weapons," the intelligence community wrote.

Putin, whose country boasts the largest arsenal of nuclear weapons in the world, has previously rattled the nuclear saber on the heels of Ukrainian advances on the battlefield.

The West, meanwhile, has described Putin's threats of using nuclear weapons as "irresponsible" and an attempt to reassert Russia's dominance in the region.

Last month, Putin upped the ante by announcing he would suspend participation in the New START treaty, a crucial nuclear arms reduction agreement. The agreement is the sole arms control treaty in place between Washington and Moscow following former President Donald Trump's withdrawal from the Intermediate-Range Nuclear Forces, or INF, treaty.

Secretary of State Antony Blinken called Putin's decision "deeply unfortunate" and said the Biden administration remains ready to negotiate "at any time with Russia, irrespective of anything else going on in the world."

What's more, Avril Haines, director of national intelligence, told lawmakers on Wednesday that Russia's military is unlikely to make "major territorial gains" this year, which could present an opportunity for additional nuclear threats.

"Putin most likely calculates that time works in his favor and that prolonging the war including with potential pauses in the fighting, might be his best remaining pathway to eventually securing Russian strategic interests in Ukraine, even if it takes years," said Haines, who leads America's 18 intelligence agencies, before the Senate Intelligence Committee.

The intelligence chiefs, who had previously warned last year that Russia would double down in Ukraine amid stalled progress, wrote that Putin's invasion has not yielded the outcome he expected and he "miscalculated the ability of the Ukrainian Armed Forces."

The spymasters also said the Russian military will continue to face personnel shortages, logistical setbacks as well as morale challenges.

Haines, who spoke alongside CIA Director William Burns, FBI Director Christopher Wray, NSA Director Gen. Paul Nakasone and DIA Director Lt. Gen. Scott Berrier, said the intelligence community continues to monitor Russia's nuclear threats.