The Pentagon is preparing for war should China, Russia, or other adversaries attack vital American satellites and other space systems, a senior Pentagon official told Congress on Wednesday.

John Rood, undersecretary of defense for policy, testified before a House subcommittee that the Trump administration's new defense policy calls for conducting military and other operations in response to space attacks, mainly by China and Russia.

Rood said American space systems are essential for "our prosperity, security, and way of life."

"And [Defense Department] space capabilities are critical for effective deterrence, defense, and force projection capabilities," he told a hearing of the House Armed Services subcommittee on strategic forces.

"Due to the critical importance of these assets, the national security strategy states, ‘any harmful interference with or attack upon critical components of our space architecture that directly affects this vital U.S. interest will be met with a deliberate response at a time, place, manner, and domain of our choosing.'"

The statement on space defense was the first clear policy announcement by a senior U.S. official outlining "declaratory policy" normally reserved for strategic nuclear weapons use.

The new policy represents a break from the policies of the Obama administration that sought to promote transparency initiatives and arms control agreements as a way to limit space weapons or conflict in space.

The policy likely will be opposed by arms control advocates, and by both China and Russia, which have been promoting agreements limiting space weapons at the United Nations while secretly building arms for space conflict.

Rood said the Pentagon has requested $12.5 billion in funding for the fiscal year 2019 that begins Oct. 1 for building up what he termed a "more resilient defendable space architecture."

The request is $1.1 billion more than funding for last year on military space.

Rood, and Air Force Gen. John Hyten, commander of the Omaha-based Strategic Command, testified on the command's budget request of $24 billion.

Neither elaborated on what space warfare capabilities are being developed. The Pentagon also has not said how it would deter and defend satellites from attack.

Space defense so far has involved development of intelligence capabilities to identify and assess if an incident in space is an attack, or the result of a malfunction or disruption due to collision with space debris.

Military space "resilience" also calls for the Pentagon to rapidly replace or restore satellites after attacks or other disruptions.

The Pentagon's Defense Science Board, in a report last year, warned that the vulnerability of U.S. satellites to electronic attack was "a crisis to be dealt with immediately."

The Joint Staff intelligence directorate warned earlier this year that China and Russia will have fully developed space attack weapons in place by 2020 that will threaten all U.S. satellites in low earth orbit—100 miles to 1,200 miles in space.

More than 780 orbiting satellites operated by 43 nations are currently in low-earth orbit and are vulnerable to electronic or kinetic attacks.

Satellites form the backbone of the U.S. military's ability to conduct combined arms warfare over long distances. They provide communications, navigation, intelligence and surveillance, weapons targeting, and attack warning.

Analysts say anti-satellites attacks knocking out 12 Global Positioning System satellites, located in medium-earth orbit around 12,550 miles high, would be severely degraded military operations.

U.S. space weapons are likely to match anti-satellite weaponry developed by both China and Russia. That would include several types of weapons and capabilities, ranging from advanced missile defense interceptors modified for space attacks on satellites, cyber warfare capabilities to disrupt or destroy anti-satellite and space weapons systems both in space and on the ground, and lasers and electronic jammers.

A defense source said one of the more stealthy anti-satellite capabilities being considered is a laser weapon capable of overheating an orbiting satellite that would disrupt or destroy electronic components.

Small satellites with robotic arms capable of maneuvering and grabbing or crushing satellites also could be developed. Such satellites have been tested by China.

The experimental space plane known as the X-37B, that has been secretly tested on long-duration flights in space, is also said to be a potential platform for delivering weapons and fighting in space.

Hyten, the Stratcom commander, said in his prepared statement that the Pentagon and National Reconnaissance Office are implementing a "space warfighting construct."

"This construct supports the national space policy and focuses on the forces, operations, and systems needed to prevail in a conflict that extends into space," he said.

"Space is a warfighting domain just like the air, ground, maritime, and cyberspace domains," Hyten said.

Currently, a defense and intelligence center called the National Space Defense Center, located at Schriever Air Force Base, Colorado, runs 24-hour operations for rapid detection, warning, and defense from space attacks.

War games involving space war also are held regularly with U.S. military forces and allies, including Asian and European allies.

Hyten also revealed that U.S. adversaries will deploy hypersonic strike vehicles—that can travel at more than 7,000 miles per hour—in the next few years.

China has conducted at least seven tests of hypersonic vehicles and Russia as well has conducted several hypersonic missile tests.

The hypersonic vehicles are designed to defeat missile defenses.

Hyten urged speeding up U.S. development of hypersonic strike weapons as well as what he termed conventional prompt strike weapons.

"New long-range, survivable, lethal, and time-sensitive strike capabilities, such as a hypersonic [conventional prompt strike] weapon, will allow the U.S. to achieve its military objectives in these environments," Hyten said. "This new weapon class prevents adversaries from exploiting time and distance and provides additional response options below the nuclear threshold."

Rood said U.S. missile defenses currently are configured for countering missile threats from North Korea and Iran and are not capable of stopping strategic strikes from China and Russia.

The undersecretary described China and Russia as the "central challenges" for the Pentagon in an increasingly complex military threat environment. "Both Russia and China are seeking to reshape the world order," he said.

Rep. Mike Rogers (R., Ala.), the subcommittee chairman, has been pressing for creation of a separate space corps within the Air Force.

Defense legislation passed last year calls for a study on the issue and for recognizing space as a warfighting domain.

"These were the first steps down a long path in the right direction," Rogers said. "Much remains to be done here to ensure we're postured to both successfully deter a conflict in space, and if need be, prevail over any adversary if a conflict extends into space."

Rogers said for space defense, the Air Force has discussed the idea of shifting from large satellites to many smaller satellites. "But what I've seen so far in the FY '19 budget isn't convincing me we're heading in that direction fast enough," he said.

As part of the Pentagon's budget for nuclear modernization, two modified nuclear weapons are planned.

One is a smaller warhead on submarine-launched ballistic missiles, to counter Russia's development of a new nuclear cruise missile in violation of the Intermediate-range Nuclear Force Treaty.

A second smaller nuclear weapon will be a new sea-launched nuclear cruise missile designed to counter China's large arsenal of medium and intermediate-range nuclear missiles.

The Pentagon also is bolstering the ground-based anti-missile interceptor force now located in Alaska and California. Twenty additional interceptors will be added to the 44 interceptors currently in place.

The added missiles are designed to counter North Korean and Iranian long-range missile threats.

Rood said the Pentagon is considering a third anti-missile interceptor base on the East Coast but has not made a final decision.

The third base will be part of the Pentagon's forthcoming Missile Defense Review that is nearing completion.

Rood said recent disclosures of new strategic nuclear capabilities by Russia were known to the Pentagon. The statements were "not surprising but disappointing," he said.

As for China, Rood warned that China is "developing a very large strategic offensive nuclear force."

"Both countries are pursuing hypersonic weapons and other capabilities and their behavior in the cyber realm concerns us," he said. "All of those things apiece are concerning and why in the national defense strategy we highlighted those two countries as our primary and central focus for our national security efforts going forward."

Asked if the U.S. doctrine of mutual assured destruction used to deter nuclear conflict with China and Russia will endure, Hyten said: "I don't think we have to worry about that for at least a decade."

U.S. strategic nuclear capabilities will remain strong enough to keep the doctrine in place, he added.

Hyten said Strategic Command is interested in developing missile defenses capable of knocking out missiles in the early stages of flight.

Direct energy and cyber attacks are two possible weapons.