By Jim Sciutto and Sean Lyngaas, CNN

(CNN) — The US has suspended operations and planning for offensive cyber operations against Russia, a senior US official told CNN.

The suspension is “a major blow,” the official said, especially since planning for such operations takes time and research to carry out. The concern, the official said, is that the pause on offensive cyber operations against Russia will make the US more vulnerable to potential cyberattacks from Moscow, which has a formidable cadre of hackers capable of disrupting US critical infrastructure and collecting sensitive intelligence.

The pause in operations and planning from US Cyber Command, the military’s offensive and defensive cyber unit, comes as the Trump administration has sought a broader détente with Russia three years into Moscow’s war against Ukraine.

Meanwhile, President Donald Trump and Vice President JD Vance berated Ukrainian President Volodymyr Zelensky in the Oval Office on Friday, throwing the US-Ukraine relationship into uncertainty.

“Due to operational security concerns, we do not comment nor discuss cyber intelligence, plans, or operations. There is no greater priority to Secretary Hegseth than the safety of the warfighter in all operations, to include the cyber domain,” a senior defense official told CNN, referring to Defense Secretary Pete Hegseth.

The Record first reported on Cyber Command’s suspension of planning related to Russia.

“It is not uncommon for the Pentagon to pause actions which are potentially destabilizing or provocative for negotiations, including cyber-effects operations,” Jason Kikta, a former Cyber Command official, told CNN. “But if a planning pause was also directed, that could cause offensive options to become stale and therefore nonviable.”

“Any extended period without checking on access and updating planning, risks losing that access or missing a critical change,” Kikta said, adding that he was not personally aware of any change in status of Cyber Command operations.

Russia and the US are in a regular state of confrontation in cyberspace, current and former US official say. The Kremlin sees cyberspace as a source of asymmetric advantage with the US, as it can burrow into US critical infrastructure and try to influence US elections.

For their part, American military and intelligence hackers have in recent years increasingly gone after Russian cybercriminals and intelligence operatives.

Since 2016, when Russia used bots, trolls and hackers to try to influence the election in favor of Trump, Moscow has repeated that playbook in some form in every US presidential election, according to US officials.

Cyber Command was established more than a decade ago, in part to respond to threats from Russia and other foreign powers. The command has matured considerably since its inception, growing into a several-thousand strong force of computer operatives who conduct offensive and defensive missions.

From its base at Fort Meade, Maryland, alongside the National Security Agency, Cyber Command has also increasingly become a tool of US power projection. The command has sent specialists to allies around the world to try to help them defend against threats from cybercriminals and spies.

That includes a trip to Ukraine in December 2021, in anticipation of Russia’s full-scale invasion, to help Kyiv prepare for an onslaught of Russian cyberattacks.

Months after Russia’s full-scale of invasion, Cyber Command confirmed that it was actively engaged in helping Ukraine defend itself through cyberattacks.

Cyber Command has also increasingly taken aim at ransomware gangs that extort US businesses for millions of dollars and threaten the safety of hospitals. Many of those gangs are based in Russia.

Cyber Command “provides people, resources and unique insights to support broader USG [US government] counter-ransomware operations,” a former senior Department of Defense official told CNN. “Russia is a permissive environment for some of the most prolific ransomware gangs and actors to operate. Does this operational planning hold apply to Russian ransomware actors that often target American companies?”

Despite the change in planning at Cyber Command, another major federal cybersecurity agency said it was not altering its posture.

The US Cybersecurity and Infrastructure Security Agency, the lead civilian agency for defending federal networks from hacks, said Sunday night on X that its mission is to “defend against all cyber threats to U.S. Critical Infrastructure, including from Russia.”

“There has been no change in our posture,” the agency said, in an apparent response to media reports that the agency was emphasizing non-Russia threats. “Any reporting to the contrary is fake and undermines our national security.”

CNN’s Natasha Bertrand contributed reporting.