The Congressional Budget Office estimates that a national missile defense system broadly aligned with President Trump's Iron Dome for America executive order would cost roughly $1.2 trillion over 20 years, far exceeding the Pentagon's publicly discussed funding plans for the initiative now known as Golden Dome for America.

In a report released today, CBO said its notional architecture would require just over $1 trillion in acquisition costs and another $166 billion in operating expenses over two decades. The largest share -- about 70% of acquisition spending -- would go toward a proposed space-based interceptor layer designed to destroy enemy missiles during the boost phase shortly after launch.

The analysis envisions a sprawling, layered homeland defense network combining 7,800 space-based interceptors, new Ground-based Midcourse Defense sites, Aegis Ashore missile-defense facilities and 35 regional defense sectors equipped with systems such as THAAD, Patriot and Glide Phase Interceptors. The architecture would also rely on extensive satellite tracking and battle-management systems.