U.S. intelligence officials believe Vladimir Putin may threaten to unleash Russia’s nuclear arsenal if Ukrainian defense forces continue to thwart his invasion of their country.

Lt. Gen. Scott Berrier, director of the U.S. Defense Intelligence Agency, revealed the concerns in a new report on global threats dated March 15 and obtained by Fox News Thursday.

"As this war and its consequences slowly weaken Russian conventional strength, Russia likely will increasingly rely on its nuclear deterrent to signal the West and project strength to its internal and external audiences," he wrote.

Defense Intelligence Agency Director Lt. Gen. Scott Berrier testifies during a House (Select) Intelligence Committee hearing on diversity in the intelligence community, on Capitol Hill in Washington, U.S., October 27, 2021.

Defense Intelligence Agency Director Lt. Gen. Scott Berrier testifies during a House (Select) Intelligence Committee hearing on diversity in the intelligence community, on Capitol Hill in Washington, U.S., October 27, 2021.  (REUTERS/Elizabeth Frantz)

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He found that Moscow’s recent adjustments to its nuclear readiness "are likely intended to intimidate," and that the Kremlin could threaten the use of "tactical, non-strategic nuclear weapons" to scare an adversary into backing down from conflict through an agreement that would be drafted in Russia’s favor.

Berrier also noted that Putin would be likely to threaten use of his nuclear arsenal as a deterrent to third parties.

Such a stance is evident in how U.S. and NATO leaders have refused requests from Ukrainian President Volodymyr Zelenskyy to impose a no-fly zone over his country that would put Western militaries in direct conflict with Russian jets.

Russian President Vladimir Putin attends a meeting of the Supreme Eurasian Economic Council in Yerevan, Armenia.

Russian President Vladimir Putin attends a meeting of the Supreme Eurasian Economic Council in Yerevan, Armenia. (Shutterstock)

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U.S. officials believe Putin intends to "overturn the U.S.-led rules based post-Cold War international order" and reclaim former Soviet territories.

"Russia views a powerful, survivable nuclear force as the foundation of its national security, and its modernized general purposes forces as critical to meet any conventional military threat and project Russian power abroad," Berrier wrote.

He noted that Russia spent that last year publicly accusing NATO of increasingly "encroaching on its borders" and finds the prospect of a Western-aligned Ukraine "unacceptable" and a "major political-military catastrophe."

However, Putin’s invasion of Ukraine has stalled after three weeks, with Ukrainian defense forces outperforming the expectations of Russian military intelligence, according to Western analysts.

The United Kingdom’s Ministry of Defense on Thursday described the Russian invasion as "faltering" due to sloppy logistics and poor planning.

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"Incessant Ukrainian counterattacks are forcing Russia to divert large numbers of troops to defend their own supply lines," the ministry said in a statement. "This is severely limiting Russia’s offensive potential."

As a result, Russian forces are increasingly using "indiscriminate methods" of attack – long-range artillery and missiles -- that are leveling cities, killing civilians and damaging infrastructure in retaliation for Ukraine’s effective resistance, according to the report.

The DIA also called into question Putin’s credibility on his claims to have "modernized" the Russian military.

Rescuers work at a site of buildings damaged by a shelling in Kyiv

Rescuers work at a site of buildings damaged by a shelling, as Russia's attack on Ukraine continues, in Kyiv, Ukraine, in this handout picture released March 17, 2022.   (Press service of the State Emergency Service of Ukraine/Handout via REUTERS )

"Russia’s modernization is intended to ensure Russia can field a military capable of engaging in the full spectrum of warfare to deter or defeat a wide scope of threats, but initial setbacks in Ukraine call some of Putin’s narrative into question," Berrier wrote.

At the same time, Russia claims it has updated more than 85% of its nuclear weapons and is working on developing missiles that are capable of circumventing Western defenses in order to "ensure that Russia can credibly inflict unacceptable damage on the West."

Putin often brags about his country’s development of fifth-generation fighter jets, according to the report.

"Russia continues to improve capabilities for its Ground Forces, Airborne Forces, and coastal troops. It is upgrading main battle tanks (MBTs) and introducing new MBTs, artillery, and multiple rocket launchers to its arsenal. Russia has also steadily increased its number of battalion tactical groups (BTGs)—the Ground Force’s primary maneuver element," Berrier wrote. "In 2021, Russia’s Defense Minister claimed its force structure could generate 168 BTGs, which is a 75 percent increase from the 96 BTGs it claimed it could generate in 2016."

Within the next decade, he warned, Russia could also field next-generation nuclear weapons including a new heavy intercontinental ballistic missile, "a transoceanic torpedo" and a new intercontinental cruise missile.

And Russia, which has a mixed record on adhering to arms control treaties, likely has a secret stash of chemical weapons, according to the report.

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"Russia almost certainly maintains biological and chemical weapon programs," Berrier wrote. "The United States Government asserts that Russia is not in compliance with its obligations under the Chemical Weapons Convention (CWC), in part because of its use of a nerve agent—referred to as Novichok—in the attempted assassination of former Russian Main Intelligence Directorate (GRU) intelligence officer Sergey Skripal and his daughter in March 2018."

Then in August 2020, Russian agent poisoned Kremlin opposition leader Alexei Navalny with the same substance. He survived -- but is currently imprisoned.