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The plan for an advanced missile defence shield over the US offers no guarantee of success and risks undermining global security.

Last week, US President Donald Trump unveiled his $175 billion plan to build the ‘Golden Dome’: a coast-to-coast missile defence shield designed to protect the US against hypersonic, ballistic, and space-based weapons. But far from enhancing US national security, the initiative risks exacerbating global instability and accelerating strategic competition.

The concept for the Golden Dome is ambitious. The proposal envisions a multi-layered defence architecture involving hundreds or even thousands of satellites in orbit, equipped with advanced sensors and interceptors, including space-based lasers. These would detect, track, and neutralize incoming missiles and other threats at various stages of flight.

In both vision and rhetoric, the plans echo Ronald Reagan’s 1983 Strategic Defence Initiative, often referred to as ‘Star Wars.’ Like the Golden Dome, the SDI proposed a layered defence system that would rely on cutting-edge, and largely untested, technologies to intercept incoming missiles before they could reach US territory. But despite years of investment, the SDI never produced a workable system and was eventually cancelled, exposing the gap between ambition and capability that still exists today.

The plan also draws inspiration from Israel’s Iron Dome system. But this comparison is misleading. Israel is much smaller than the US, and its Iron Dome protects the country from short-range, unguided rockets – threats that are limited in number, speed, and direction. Trump’s plan, by contrast, seeks to defend the entire US homeland from far more advanced and numerous threats, including long-range ballistic missiles, hypersonic glide vehicles and orbital delivery systems. The scale, complexity, and technical sophistication required are of a completely different order.

Costs – and risks

Despite Trump estimating that the system will cost $175 billion and could be built in just three years, the Congressional Budget Office has warned that the space-based components alone could cost as much as $542 billion to deploy and operate over the next 20 years. Fundamental questions remain unanswered: what the system will look like, who will build it, and whether it will function as intended.

Investing the necessary resources to develop such an advanced system would require significant trade-offs that could come at the expense of other defence priorities. 

The US does not currently have the full spectrum of technology it needs to intercept hypersonic or ballistic missiles in space, which would require interceptors or lasers capable of operating over vast distances with near-instant precision. Pursuing the Golden Dome risks prioritising an expensive and unproven system over more immediate and achievable capabilities, such as improving regional missile defences and cyber resilience to countering emerging threats like drones.

The plan also has potentially dangerous strategic consequences. A system that aspires to make the US invulnerable to missile attack would almost certainly be seen by its adversaries as an attempt to undermine the logic of nuclear deterrence. If Washington is perceived to be developing a shield that could one day neutralize a retaliatory nuclear strike, it risks triggering a dangerous global arms race.

Beijing and Moscow have already criticized the Golden Dome project as ‘deeply destabilizing’ and could respond with a range of countermeasures, including expanding their offensive arsenals or developing new delivery systems. This arms race could also incentivize the deployment of space-based weapons at a time when space remains dangerously under-regulated. The Golden Dome could therefore undermine global security, making the world a more dangerous place – including for the US.

Leverage for diplomacy?

Given these risks, the US should instead use the Golden Dome plan as leverage to launch renewed arms control diplomacy. Washington should use the proposal to reinitiate dialogue with other major powers, including Russia and China, on mutual restraint, transparency, and the governance of emerging missile and space-based technologies. 

This is especially urgent given the deterioration of existing arms control frameworks. The last major arms control agreement between the US and Russia, the New START Treaty, was suspended by President Vladimir Putin in 2023. It is set to expire in 2026 with no successor in place. Despite China’s growing arsenal, arms control talks between the US and China were also suspended in July 2024 over US arms sales to Taiwan.

Meanwhile, rapid advances in missile technology, space systems, and artificial intelligence are outpacing the rules and norms designed to manage them. As geopolitical tensions rise, so does the risk of miscalculation and escalation. The need to revive strategic dialogue is therefore more pressing than ever.

While China and Russia may be sceptical of US intentions, the Golden Dome’s space-based elements could create a rare opportunity for renewed arms control dialogue on space security. This might not necessarily focus on warhead reductions, but on more immediate and achievable areas of shared concern. 

Space security

Space security is one of the most promising and necessary avenues for engagement. As nuclear-armed powers become increasingly reliant on space-based systems for both military and civilian purposes (from early warning systems and communications to navigation and surveillance), the risks of miscalculation or unintended escalation in orbit are growing.

A pragmatic and urgently needed step would be to launch dialogue on the norms that should govern behaviour in space, including avoiding close approaches to satellites, limiting the deployment of certain space-based systems, or improving transparency.

Even modest measures, such as agreeing to share notifications of satellite launches or discussing dual-use capabilities, could help to build trust and reduce the likelihood of conflict in orbit. By focusing on space, where interests overlap and mutual vulnerabilities are clear, the US could help to re-establish the foundations for wider future strategic dialogue. 

Avoiding past mistakes

In the 1980s, Reagan’s SDI consumed vast resources, heightened international tensions, and failed to deliver a functioning defence system. It also contributed to an arms race that left the world more divided, not more secure. The Golden Dome risks repeating those same mistakes, but with more players, faster technologies, and fewer guardrails in place.

At a time when arms control frameworks are crumbling and global tensions are rising, the announcement of the Golden Dome should be seen as a strategic opportunity to initiate renewed discussions on space security. Framing the proposal as a starting point for dialogue, rather than a signal of unilateral ambition, could help to stabilize a dangerously volatile moment. Otherwise, the project risks pushing the world one step further towards a more contested, militarized, and insecure future.