Iran War Costs Reach $43.6 Billion by the Pentagon's Count as Congress Stalls on Funding and Interceptor Stocks Run Low
The Pentagon’s latest estimate puts the cost of the war with Iran at $43.6 billion as of 3 September. Of that, $11.2 billion has been spent on operations and $32.4 billion is the cost of replacing munitions and equipment, which hasn’t been funded. The figure leaves out repairs to bases in eight countries.
Every estimate so far has been overtaken by the next. The Defense Department’s inspector general counted $33.4 billion through June. Defense Secretary Pete Hegseth told Congress in July the war would cost $37.5 billion through September. CBO, in a letter on 15 September, put the cost through 1 August at about $38 billion, with $2 billion to $3 billion more each month.
Eight months in
US and Israeli strikes on Iran began on 28 February 2026. A ceasefire in April and a memorandum in June both broke down, the second in July after Iranian attacks on shipping in the Strait of Hormuz. A US naval blockade of Iranian ports has been in place since April.
On 9 October the Pentagon raised its official count of US casualties to 21 dead and 865 wounded. The President said on 8 October that the US would not attack Iran before the 3 November midterms. About 20,000 US troops and at least three carrier strike groups remain in the region.
The munitions problem
CBO’s letter is the most detailed public accounting. Munitions make up $21.7 billion of its estimate. Interceptors, the missiles that shoot down Iranian missiles and drones, account for $13.1 billion. Each THAAD interceptor costs about $12 million and each SM-3 about $28 million.
CBO estimates the US has used between half and two-thirds of its interceptor inventory since June 2025, counting the strikes on Iran that year. Rebuilding the stock will take at least five years at current production rates. That affects more than Iran: the same interceptors are what Ukraine and Gulf partners want, as covered in our arms sales post.
Congress hasn’t paid
The White House asked for an $87.6 billion supplemental in June, $67.1 billion of it for the Pentagon. CBO says about $42.3 billion of the defence portion appears directly related to the war. Congress hasn’t passed it.
Republicans have tried to fund the war through reconciliation instead, which avoids the Senate filibuster. The House adopted a budget resolution for a $95 billion package in July. The Senate version stalled, as covered in our reconciliation post. For now the Pentagon is paying from its regular accounts, which run on the stopgap to 11 December.
War powers
The Constitution gives Congress the power to declare war, and the 1973 War Powers Resolution requires the President to withdraw forces after 60 days without authorisation. Congress has voted repeatedly on the Iran war. The House passed a resolution 215 to 208 on 3 June, and the Senate adopted it in late June by 50 to 48. Because it was a concurrent resolution, it didn’t go to the President and has no binding effect. On 24 September a further Senate attempt failed 49 to 50. The Senate has voted 14 times.
Why it matters
The war’s cost is modest next to a $1 trillion defence budget, and next to $1.14 trillion in annual interest. The harder limit is physical. Interceptors take years to build, and every one fired at Iran is unavailable for Taiwan or Europe. The December spending deal is where Congress decides whether to pay for replacements, and how fast.