By Zachary Cohen and Oren Liebermann, CNN

(CNN) — US military officials are scrambling to develop a “Golden Dome” defense system that can protect the country from long-range missile strikes and have been told by the White House that no expense will be spared in order to fulfill one of President Donald Trump’s top Pentagon priorities, according to multiple sources familiar with the matter.

“Golden Dome” is the Trump administration’s attempt to rebrand vague plans for developing a missile defense system akin to Israel’s Iron Dome.

At a time the Pentagon is looking to cut budgets, the Trump administration has ordered military officials to ensure future funding for “Golden Dome” is reflected in new budget estimates for 2026 to 2030 – but the system itself remains undefined beyond a name, the sources said.

“Right now, Golden Dome is, it’s really an idea,” one source familiar with internal discussions about the project said, adding there may be technology in the pipeline that, if ever scaled up, could apply to it, but as of now discussions are purely conceptual.

That makes projecting future costs nearly impossible, the source added, though it would likely cost billions of dollars to construct and maintain.

Trump has repeatedly insisted the US needs a missile defense program similar to Israel’s Iron Dome, but the systems are orders of magnitude apart. In practical terms, the comparison is less apples to oranges, and more apples to aircraft carriers.

Israel’s Iron Dome missile defense system selectively protects populated areas from short-range threats in a country the size of New Jersey; Trump wants a space-based missile defense system capable of defending the entire United States from advanced ballistic and hypersonic missiles.

For one thing, “Israel is tiny,” the source familiar with ongoing internal discussions about the Golden Dome project said. “So, it is 100% feasible to blanket Israel in things like radars and a combination of mobile and fixed interceptors.”

“How are you going to do that in the United States? You can’t do it just at the borders and the shoreline, because intercontinental ballistic missiles, they can re-enter the atmosphere over Kansas.”

Still, Trump issued an executive order during his first week in office ordering Defense Secretary Pete Hegseth to submit a plan for developing and implementing the next-generation missile defense shield by March 28.

And a senior Pentagon official insisted earlier this week that work is underway.

“Consistent with protecting the homeland and per President Trump’s [executive order], we’re working with the industrial base and [through] supply chain challenges associated with standing up the Golden Dome,” Steven J. Morani, currently performing the duties of undersecretary of defense for acquisition and sustainment said this week at the McAleese Defense Programs Conference in Washington.

At the same time, Pentagon officials have been realigning the Defense Department’s 2026 budget proposal to meet Hegseth’s priorities, which were outlined in a memo delivered to senior leaders last week and represents a major overhaul of the military’s strategic goals, according to a copy obtained by CNN.

The memo specifically directs Pentagon leadership to focus on strengthening missile defense of the US homeland through Trump’s “Golden Dome.”

“There is a rigorous analytic process underway taking a relook at [the budget],” Morani added. “This is standard practice for any new administration that takes office.”

But it remains unclear how much money the Pentagon will request for Trump’s Golden Dome in its budget proposal or how officials will determine the amount of funding is required.

Retired Rear Adm. Mark Montgomery believes creating a ballistic missile defense system may be possible in 7-10 years, but even then, it will have severe limitations, potentially capable of protecting only critical federal buildings and major cities.

“The more you want it closer to 100%, the more expensive it’s going to get,” said Montgomery, the senior director of the Center On Cyber and Technology Innovation at the Foundation for Defense of Democracies.

A comprehensive system will require different sets of satellites for communication, sensing incoming missiles, and launching interceptors, Montgomery told CNN. Those types of systems are long-term projects, he said, requiring existing defenses to fill the gap in the meantime.

“You’ve gotta be responsible here,” Montgomery said. “You’re not going to be able to defend everything with these ground-based missiles. They defend a circle around them, but it’s not large.”

Potential pay day for arms companies

US arms manufacturers are already seeing dollar signs. The Missile Defense Agency held an Industry Day in mid-February to solicit bids from companies interested in helping to plan and build Golden Dome.

The agency received more than 360 secret and unclassified abstracts about ideas for how to plan and execute the system.

Lockheed Martin has taken it a step further, creating a polished website for Golden Dome claiming the world’s largest defense contractor has the “proven, mission-tested capabilities and track record of integration to bring this effort to life.”

In the 1980s, President Ronald Reagan announced the Strategic Defense Initiative to create a space-based defense against ballistic nuclear missiles. The system was derisively nicknamed “Star Wars,” and consumed tens of billions of dollars before it was ultimately cancelled, facing insurmountable technical and economic hurdles.

Laura Grego, a Senior Research Director of the Global Security Program at the Union for Concerned Scientists, says the same challenges remain and have been known for years.

“It has been long understood that defending against a sophisticated nuclear arsenal is technically and economically unfeasible,” Grego told CNN.

America’s current ballistic missile defense is designed to thwart a small number of missiles from a rogue state such as North Korea or Iran. The system relies on the Ground-based Midcourse Defense (GMD), which has failed nearly half of its tests, according to the Arms Control Association, rendering it incapable of stopping a major attack from Russia or China.

But in his executive order, Trump called for a far more complex and robust system - space-based interceptors capable of downing a target moments after it launches.

Such a system would require thousands of interceptors in low-earth orbit to intercept even a single North Korean missile launch, according to the American Physical Society (APS), which has studied the feasibility of ballistic missile defenses for years. A single interceptor in orbit is almost never at the right place and time to rapidly intercept a ballistic missile launch, so you need exponentially more to ensure adequate coverage.

“We estimate that a constellation of about 16,000 interceptors would be needed to attempt to counter a rapid salvo of ten solid-propellant ICBMs like the [North Korean] Hwasong-18,” the APS wrote in a study earlier this month.

Even then, Grego says a space-based missile defense system is vulnerable to enemy anti-satellite attacks from far less expensive ground-based systems.

“The most critical weakness of a system like this is its brittleness, its vulnerability to attack,” Grego added.

In the Red Sea, the US has fired scores of multi-million dollar interceptor missiles at Houthi drones and missiles that cost a fraction of the price. The fiscal imbalance gets far worse when the system is in space, according to John Tierney, a former Democratic congressman who held years of hearings on ballistic missile defense.

“It’s a joke. It’s basically a scam,” Tierney said bluntly. Now the executive director for the Center for Arms Control & Non-Proliferation, Tierney ripped Trump for being “willing to throw billions and billions and billions of dollars at something that won’t work.”

Adversaries likely to react

As the US pours money into research and developing the Golden Dome, current and former officials say America’s adversaries will likely expand their own arsenal of ballistic missiles in an effort to stay ahead.

But since the offensive ballistic missiles are far less expensive than the interceptors needed to stop them, Tierney says the system quickly becomes financially unfeasible.

US military officials are also assessing how Golden Dome could disrupt the current stability provided by nuclear deterrence, according to the source familiar with internal planning discussions related to the project.

Today, the main US deterrent against another country launching a preemptive nuclear attack is its survivable second strike, or ability to retaliate even after enduring an initial nuclear attack, the source said.

“If you implement something that your nuclear armed adversaries believe is a reliable countermeasure that just nullifies their nuclear arsenal, now you’ve done away with deterrent stability, because you’ve improved the ease of the United States sending a nuclear attack to them with impunity,” the source added. “And then you have to ask yourself, well, how much do we trust the US not to do that?”

“If I’m China, if I’m Russia, my confidence is lower and lower, that that the US won’t strike us with a nuclear missile in in a crisis,” according to the same source.

“Strategically, it doesn’t make any sense. Technically, it doesn’t make any sense. Economically it doesn’t make any sense,” Tierney added.

CORRECTION: An earlier version of this story incorrectly attributed a quote about the comprehensive system necessary to provide the kind of protection President Donald Trump has asked for. Retired Rear Adm. Mark Montgomery said, “You’ve gotta be responsible here. You’re not going to be able to defend everything with these ground-based missiles. They defend a circle around them, but it’s not large.”

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