The ongoing United States–Israeli military campaign against Iran has already cost Washington an estimated $3.7 billion in its first 100 hours, according to new research from the Washington-based think tank Center for Strategic and International Studies (CSIS). The study suggests the war is costing the United States nearly $900 million per day, largely due to the heavy use of advanced weapons and military operations. Researchers Mark Cancian and Chris Park reported that only a small portion of the total cost had been included in the Pentagon’s existing budget. Of the $3.7 billion spent during the first 100 hours of the conflict, roughly $3.5 billion was not previously budgeted, meaning the Department of Defense will likely need to request additional funding soon.
The authors noted that this request could become politically controversial for the Trump administration. Rising domestic concerns over inflation, living costs, and higher gasoline prices tied to the conflict could weaken public support for the war. The issue is also creating divisions within Trump’s “America First” political base, which has traditionally opposed prolonged foreign conflicts. Because the Department of Defense has released limited operational details, the researchers based their estimates on Congressional Budget Office (CBO) data regarding operational costs, adjusting for inflation and increased military activity. Their analysis suggests that more than 2,000 munitions were used during the first 100 hours of fighting, and replacing those weapons could cost about $3.1 billion, with replenishment costs increasing by roughly $758 million per day.
U.S. Defense Secretary Pete Hegseth has indicated that American military operations may expand further, with additional fighter squadrons, defensive systems, and bomber deployments expected. Meanwhile, the human toll of the conflict continues to rise. Iranian authorities report more than 1,300 deaths, including at least 181 children, while additional casualties have been reported in Lebanon, Israel, Gulf Arab states, and among U.S. forces.
