“Of the US$1.2 trillion amount, acquisition costs…would total just over US$1 trillion. That amount includes costs for the system’s major components – namely, the interceptor layers and a space-based missile warning and tracking system,” the CBO said in a report.

“The most expensive component is the space-based interceptor layer, which accounts for about 70% of acquisition costs and 60% of total costs,” it said.

Average annual costs for operations and support would meanwhile come in at US$8.3 billion, the report said.

Trump ordered the Pentagon to develop plans for a high-tech missile defence shield in late January 2025, initially dubbing it “Iron Dome for America”.

In May 2025, Trump announced that US$25 billion had been earmarked for the project, estimating its total cost at US$175 billion.

However, CBO said the same month that the cost of space-based interceptors to defeat a limited number of intercontinental ballistic missiles could be between US$161 billion and US$542 billion over 20 years.

And the goals for Golden Dome are significantly more expansive, with the 2026 National Defense Strategy saying the Pentagon will “focus on options to cost-effectively defeat large missile barrages and other advanced aerial attacks”.