CBO Says $38 Billion Iran Conflict Could Leave Five-Year Missile Gap

$38 billion is the Congressional Budget Office’s estimate of U.S. military costs from combat operations against Iran through Aug. 1. The more durable constraint, however, may be measured in years: CBO estimates that operations since June 2025 consumed between one-half and two-thirds of the combined U.S. inventory of Patriot, Terminal High Altitude Area Defense, Standard Missile-3 and Standard Missile-6 interceptors.

Rebuilding those defensive-missile stocks could take at least five years even if production increases. That turns the conflict’s immediate bill into a longer readiness problem for deployed U.S. forces, allies relying on American missile defenses and taxpayers expected to finance replacement orders.

Most of the replacement bill is tied to munitions

CBO put the cost of replacing expended munitions at $21.7 billion. Missile-defense interceptors account for $13.1 billion of that figure, compared with $7.3 billion for land-attack cruise missiles and $1.2 billion for other munitions.

The estimated unit prices help explain why defensive expenditure accumulates so quickly. CBO used approximate costs of $4 million for a Patriot interceptor or SM-6, $12 million for a THAAD interceptor and $28 million for a sophisticated SM-3. These are specialized guided weapons built to meet demanding interception requirements, not commodity items that factories can replace quickly after a surge in use.

The remaining cost estimate extends beyond missiles. CBO attributed $10.4 billion to increased flying hours, $2.7 billion to fuel and $1.9 billion to replacing battle losses, including a destroyed THAAD radar. Its $38 billion total excludes costs incurred by other federal agencies and military operating expenses that were already included in the federal budget, so it is not a complete all-government accounting of the conflict.

The inventory estimate has a major uncertainty

The Pentagon does not publicly disclose the relevant interceptor inventories and did not respond to CBO’s information requests. CBO therefore compared reported missile expenditures with cumulative Defense Department purchases to estimate the share consumed. The agency explicitly cautioned that the result carries considerable uncertainty.

That method does not provide the same confidence as a verified count of usable missiles. Cumulative purchases can establish an outer reference point, but the public figures do not directly reveal how many rounds remained available before the conflict. Still, the estimated depletion range is large enough that even its lower bound half of the combined inventory—points to a substantial replenishment burden.

Combining four interceptor families also requires care. Patriot, THAAD, SM-3 and SM-6 are not interchangeable rounds pulled from one common bin. They support different launch systems and defensive roles. A combined depletion estimate is useful for showing the scale of expenditure, but it cannot identify the condition of each individual inventory without data the Pentagon has not released.

Money cannot instantly convert into missiles

The five-year estimate reflects an industrial constraint as much as a budget problem. Missile output depends on qualified suppliers, specialized materials, solid rocket motors, electronics, testing capacity and skilled labor. Adding funds can support new tooling, facilities and hiring, but those changes still require contracts, supplier qualification and production ramp-up time.

A CSIS assessment of the air- and missile-defense industrial base argues that stable multiyear demand is necessary before manufacturers commit capital and expand workforces. It also identifies shared constraints including motors, energetics, seekers, electronics, actuators and test infrastructure that can affect several missile programs at once. That matters because ordering more completed interceptors does not by itself expand the slowest supplier beneath the prime contractor.

Recent production initiatives show the scale of the intended response, but also its timing. The fiscal 2027 defense request includes unusually large quantities and funding for missile defense, including Patriot and THAAD interceptors. Those requested purchases would need congressional funding and successful industrial execution; a procurement plan is not the same as delivered inventory.

The tradeoff is therefore broader than replacing rounds already used. Missiles coming off expanded lines may be needed simultaneously to refill U.S. stocks, support deployed forces and satisfy allied demand. Until production catches up, allocating a limited flow among those requirements can shift risk rather than eliminate it.

A continuing monthly cost

CBO estimated that continued fighting at relatively low intensity would add roughly $2 billion to $3 billion per month, with higher costs possible if operations intensify. Continued interceptor expenditure would also move the replenishment target while factories are trying to reach it.

The immediate public bill is large, but the production lag is the harder constraint: the government can approve replacement funding faster than industry can deliver complex interceptors. CBO’s estimate indicates that closing the resulting missile gap may extend to at least 2031, even with higher output.

By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.