A missile defence shield proposed by US President Donald Trump could cost more than $1 trillion over two decades, according to a report by the Congressional Budget Office (CBO) published on Tuesday.
The independent budget watchdog estimated total costs for the "Golden Dome" at around $1.2 trillion over 20 years, including roughly $1 trillion in procurement costs alone.
More than two-thirds of those procurement costs would stem from the space-based component of the system, the report said.
Trump launched the project at the start of his second term, modelling it on Israel's "Iron Dome" defence shield but envisioning a much broader system capable of intercepting not only short-range missiles but also modern hypersonic and long-range missiles from both the air and space.
The proposed system would significantly expand beyond existing US missile defence capabilities.
Trump said last year that an initial $25 billion had been earmarked to launch the project and estimated total costs at about $175 billion.
The CBO based its estimates on an executive order Trump signed shortly after taking office. Under that framework, the system would include regional and nationwide ground-based defences as well as satellite-based interception capabilities.
