The U.S. military has “probably used” between half and two thirds of its missile defense interceptors during the war with Iran, according to a Congressional Budget Office report.
That depletion could hamper American efforts to defend Taiwan if China launched an invasion, the report warned.
The report, released Tuesday, delivered a grim assessment of the nation’s remaining munitions.
It was prepared after Rep. Brendan F. Boyle, the ranking member of the House Committee on the Budget, requested cost estimates for combat operations against Iran.
“The main opportunity cost of the conflict thus far has been the large expenditure of missile defense interceptors, which will leave the United States with a reduced inventory of interceptors for several years,” officials wrote in the report.
“The shortfall would become especially problematic if a conflict arose with an opponent whose arsenal included large numbers of ballistic and cruise missiles,” officials continued.
“(The People’s Republic of China, PRC, maintains such an arsenal, which would probably play a major role in a military conflict involving Taiwan.)”
The report focused on the use of missile defense interceptors such as Patriot and Terminal High Altitude Area Defense interceptors. It concluded that the “large expenditure” of those weapons would reduce the American inventory for years.
Replacing the “costly” interceptors “would probably take at least five years,” according to the report.
A military conflict with China during that period could place even “greater stress” on U.S. defense efforts.
The warning arrives as the War Department increasingly emphasizes missile defense as its primary deterrent against China in the Indo-Pacific region. Earlier this year, the United States moved missile defense systems from South Korea as missiles were shifted from the region to support operations in the Middle East.
American missile interceptors have primarily been used to defend U.S. and allied assets from Iranian ballistic missile attacks, according to the Congressional Budget Office.
The report said “significant quantities” of some munitions were used to protect Israel against Iranian ballistic missiles in June 2025.
The Wall Street Journal reported that the United States fired nearly 150 Terminal High Altitude Area Defense interceptors and 80 Standard Missile-3 interceptors during those defense operations. Those expenditures represented a substantial draw on weapons that the budget office said will take years to replace.
“Operation Epic Fury has reduced those inventories further,” officials wrote. Operation Epic Fury is the Pentagon’s name for the initial combat operations against Iran that reportedly ended in May.
In July, the DoW began describing combat connected to the Iran war as “overseas operations.”
Reports about shrinking munitions stockpiles had already circulated in the defense community for months, with experts raising concerns as early as the first week of the war.
President Donald Trump rejected concerns about severe depletion in August.
He told Forbes that the United States possessed “massive amounts” of munitions and said manufacturers were already producing more.
The Congressional Budget Office estimated that the Iran war has cost the War Department nearly $38 billion. That total exceeds the $33.4 billion estimate released Monday by the Pentagon Inspector General.
The budget office’s estimate included efforts to replenish missile defense interceptors, cruise missiles used for attacks on land, and other munitions consumed during operations involving Iran between Feb. 29 and Aug. 1.
Replacing those supplies could cost as much as $21.7 billion, the report estimated.
Those calculations carry a major caveat. The report’s authors said the estimates “are subject to considerable uncertainty” because the Department of War did not respond to information requests, forcing congressional analysts to rely on government databases and public reports.
The cost estimate excludes damage to bases, routine Navy ship deployments, future equipment maintenance, medical supplies, and other personnel expenses. It also excludes future health care costs after separation for veterans injured during operations involving Iran.
Combat operations against Iran remain underway, meaning the War Department’s costs continue to rise.
The budget office estimated that one additional month of conflict could cost between $2 billion and $3 billion, depending on the intensity of strikes and combat flight hours.
