The Pentagon is rushing to expand its capacity to wage war in space, convinced that rapid advances by China and Russia in space-based operations pose a growing threat to U.S. troops and other military assets on the ground and American satellites in orbit.

Details of the push by the Pentagon remain highly classified. But Defense Department officials have increasingly acknowledged that the initiative reflects a major shift in military operations as space increasingly becomes a battleground.

No longer will the United States simply rely on military satellites to communicate, navigate and track and target terrestrial threats, tools that for decades have given the Pentagon a major advantage in conflicts.

Instead, the Defense Department is looking to acquire a new generation of ground- and space-based tools that will allow it to defend its satellite network from attack and, if necessary, to disrupt or disable enemy spacecraft in orbit, Pentagon officials have said in a series of interviews, speeches and recent statements.

The strategy differs fundamentally from previous military programs in space by expanding the range of offensive capabilities — a far cry from the never-built 1980s-era Strategic Defense Initiative proposal, for example, which was focused on using satellites to protect the U.S. from nuclear missile strikes.

“We must protect our space capabilities while also being able to deny an adversary the hostile use of its space capabilities,” Gen. Chance Saltzman, the chief of space operations at the Space Force, the agency created in 2019 as a new division of the Air Force Department to lead the effort, said in March. “Because if we do not have space, we lose.”

Pentagon officials and a recent unclassified assessment by the director of national intelligence say that both Russia and China have already tested or deployed systems such as ground-based high-energy lasers, antisatellite missiles or maneuverable satellites that could be used to disrupt American space assets.

The concern has only escalated with reports that Russia may be developing a space-based nuclear weapon that could broadly wipe out satellites in orbit, both commercial and military. Russia’s use of electronic jamming tools during the war in Ukraine — which have at times disrupted advanced American weapons systems — is cited by Pentagon officials as another reason the United States must intensify its defenses in space.

“It is now not theoretical,” Gen. Stephen N. Whiting, who oversees Space Command, which is responsible for using space assets to defend the United States, said in a meeting with reporters last month during a space industry conference in Colorado. “It’s real. It’s deployed, out in the environment.”

But the move to enhance warfighting capacity in space is driven mostly by China’s expanding fleet of military tools in space.

“China has fielded a number of space capabilities designed to target our forces,” Air Force Secretary Frank Kendall said in an interview. “And we’re not going to be able operate in the Western Pacific successfully unless we can defeat those.”

General Whiting said China had tripled its network of intelligence, surveillance and reconnaissance satellites since 2018, which he described as a “kill web over the Pacific Ocean to find, fix, track and, yes, target United States and allied military capabilities.”

Government officials in China and Russia have rejected these assertions, arguing that it is the United States that is driving the militarization of space.

“The United States has long been repeatedly hyping up China as a ‘threat in outer space’ to smear and attack China,” said a Chinese government statement issued earlier this year, calling this effort “only an excuse for the U.S. to expand its forces in outer space and maintain military hegemony.”

In pushing back against American claims, Russia and China unsuccessfully urged the United Nations Security Council last month to “to prevent for all time the placement of weapons in outer space.”

John F. Plumb, assistant secretary of defense for space policy, called the Russian and Chinese proposal — made after the United States pushed for a resolution reiterating that nuclear weapons should not be deployed in space — impossible to verify and enforce and “hypocritical because both Russia and China are deploying weapons.”

Militarization of space is unavoidable, he added.

“The history of humanity is where there are military advantages, the military will operate,” Mr. Plumb said in an interview. “People will try to neutralize those advantages and try to exploit those advantages. And space is no different.”

American officials are instead moving ahead with an effort they are calling “responsible counterspace campaigning,” an intentionally ambiguous term that avoids directly confirming that the United States intends to put its own weapons in space.

But it also is meant to reflect this commitment by the United States to pursue its interest in space without creating massive debris fields that would result if an explosive device or missile were used to blow up an enemy satellite. That is what happened in 2007, when China used a missile to blow up satellite in orbit. The United States, China, India and Russia all have tested such missiles. But the United States vowed in 2022 not to do any such antisatellite tests again.

The United States has also long had ground-based systems that allow it to jam radio signals, disrupting the ability of an enemy to communicate with its satellites, and is already taking steps to modernize these systems.

But under its new approach, the Pentagon is moving to take on an even more ambitious task: broadly suppress enemy threats in orbit in a fashion similar to what the Navy does in the oceans and the Air Force in the skies.

One of the top priorities is so-called force protection, meaning the ability of the Space Force to ensure that other branches of the military are not threatened as a result of enemy use of satellites to find and target them before their units reach a battlefield.

“Achieving space superiority through effective suppression of enemy space capabilities” is how a recently updated Pentagon war fighter doctrine describes this tactic.

Given how classified this work is, Pentagon officials declined to discuss the details. Aides to General Saltzman canceled a planned interview with The New York Times after they were told that he would be asked about specific warfighting tools.

“There’s value in ambiguity so potential competitors and strategic competitors have to figure out what we’re doing,” General Whiting said when separately asked by The Times about the Space Force’s efforts.

But there are hints, including a recent report drafted by Charles S. Galbreath, a former Space Force colonel. He cited three examples that could disable enemy satellite networks: cyberattacks, ground or space-based lasers, and high-powered microwaves.

One Pentagon-funded report, as far back as the 1990s, proposed building a space-based “hunter killer” satellite that would send a beam of high energy toward enemy satellites to burn out their electronics, predicting that it could be part of Air Force operations as of 2025.

John Shaw, a recently retired Space Force lieutenant general who helped run the Space Command, agreed that directed-energy devices based on the ground or in space would probably be a part of any future system.

“It does minimize debris; it works at the speed of light,” he said. “Those are probably going to be the tools of choice to achieve our objective.”

The United States has never confirmed publicly that it has space-based weapons.

Pentagon leaders declined to discuss any specifics, other than to say that by 2026 they intended to have “substantial on-orbit capability that allows us to compete in full-spectrum operations,” as General Saltzman described the plan to Senate lawmakers last year, hinting at offensive capabilities.

But the Pentagon also already has its secretive X-37B, a crewless Space Shuttle-like space plane that has already flown seven missions, leading to speculation that it might be designed as a weapons platform. Military officials have said it is being used for experiments.

The Pentagon is separately working to launch a new generation of military satellites that can maneuver, be refueled while in space or have robotic arms that could reach out and grab — and potentially disrupt — an enemy satellite.

Another early focus is on protecting missile defense satellites. The Defense Department recently started to require that a new generation of these space-based monitoring systems have built-in tools to evade or respond to possible attack. “Resiliency feature to protect against directed energy attack mechanisms” is how one recent missile defense contract described it.

Last month the Pentagon also awarded contracts to two companies — Rocket Lab and True Anomaly — to launch two spacecraft by late next year, one acting as a mock enemy and the other equipped with cameras, to pull up close and observe the threat. The intercept satellite will not have any weapons, but it has a cargo hold that could carry them.

General Saltzman said he was trying to reduce the vulnerability of the United States to a space-based attack.

“Avoiding operational surprise requires us to maintain an accurate understanding of the space domain at all times,” he told Senate appropriators last month, adding that about $2.4 billion of the proposed $29.4 billion Space Force budget for 2025 was set aside for “space domain awareness.”

Because the programs are classified, no one outside of the government can reliably estimate how much is being spent cumulatively on systems designed to disrupt or disable enemy space assets. But Todd Harrison, an aerospace engineer who studies the military space budget at the conservative American Enterprise Institute, said it was likely hundreds of millions of dollars a year.

Even with that, Mr. Harrison said, it will probably be five to 10 years before the United States has a substantial suite of offensive weapons in space, assuming such an effort moves ahead.

Others contend that the United States itself is pushing too hard to turn space into a warfighting zone.

“This is a quest for domination by the U.S.,” said Bruce Gagnon, a longtime peace activist from Maine who has called for a ban on all weapons in space

The Pentagon is hardly deterred. It is working to coordinate its so-called counterspace efforts with major allies, including Britain, Canada and Australia, through a multinational operation called Operation Olympic Defender.

France has been particularly aggressive, announcing its intent to build and launch by 2030 a satellite equipped with a high-powered laser.

Despite this combined effort, there is agreement among officials in the Pentagon and in Congress that the Space Force is not moving fast enough.

“We’re not acquiring the counterspace capabilities at the pace we need to fight and win in space,” Representative Mike Rogers, Republican of Alabama and the chairman of the House Armed Services Committee, said at an Air Force budget hearing last month.

But what is clear is that a certain threshold has now been passed: Space has effectively become part of the military fighting domain, current and former Pentagon officials said.

“By no means do we want to see war extend into space,” Lt. Gen. DeAnna M. Burt, deputy chief of space operations, said at a Mitchell Institute event earlier this year. “But if it does, we have to be prepared to fight and win.”