A new analysis has revealed that the United States–Israel war on Iran is costing the U.S. government an estimated $3.7 billion within just the first 100 hours of conflict, averaging nearly $900 million per day. The report, produced by the Center for Strategic and International Studies (CSIS), highlights that the overwhelming majority of these expenses—about $3.5 billion—are not included in existing Pentagon budgets, raising concerns that additional emergency funding will soon be required.
Researchers Mark Cancian and Chris Park noted that the high costs are primarily driven by the rapid use of advanced munitions, including stealth bomber operations, missile systems, and air defense interceptors. More than 2,000 weapons have reportedly been expended in the early phase of the war, with replacement costs alone estimated at over $3.1 billion. They warn that if the conflict continues at this pace, daily military spending could rise by an additional $758 million or more.
The study suggests that the Pentagon may soon seek supplemental appropriations from Congress, similar to funding requests made during earlier large-scale conflicts such as Iraq and Afghanistan. However, analysts caution that securing additional funding could face political resistance, especially given rising concerns over inflation, the national debt, and domestic economic pressures.
Defense Secretary Pete Hegseth has indicated that military operations are expected to intensify, with more fighter deployments, bomber missions, and defensive systems being activated. Analysts say this could further increase costs, even if air campaign intensity eventually stabilizes.
The financial burden is already influencing political debate in Washington. Lawmakers are reportedly surprised by the scale of expenditures, and a potential $50 billion supplemental request to replenish missiles and defense systems could face scrutiny in Congress. Some legislators worry that the war’s cost will become a major point of political contention.
Beyond financial implications, the conflict has resulted in significant human casualties. Reports estimate more than 1,300 deaths in Iran, including civilians and children, alongside casualties in Lebanon, Israel, and Gulf states. At least six U.S. service members have also been killed.
Overall, the report underscores both the staggering economic cost and the growing humanitarian toll of the conflict, suggesting that the war’s financial and political consequences may expand significantly if fighting continues.
