Cost to US for war on Iran is $3.7bn in first 100 hours, says think tank

Most of the costs are not budgeted for, meaning the Pentagon will need to request more funding soon, researchers say.A US B-2 bomber, like those used in the ongoing attacks in Iran, returns from a massive strike on Iranian nuclear sites last year [File: David Smith/AP]Published On 6 Mar 2026The United States-Israeli war on Iran is estimated to have cost Washington $3.7bn so far in its first 100 hours alone, or nearly $900m a day, driven largely by the huge expenditure of munitions, according to new research.An analysis by Washington-based think tank the Center for Strategic and International Studies (CSIS) underlined the colossal cost of the war, which entered its seventh day on Friday, as the US attacks Iran with stealth bombers and advanced weapons systems.Recommended Stories list of 4 itemslist 1 of 4US says Iran missile attacks down 90% after strikes from B-2 bomberslist 2 of 4Iran targets Israeli embassy in Bahrain, Al Udeid Air Base in Qatarlist 3 of 4Iran war: What is happening on day seven of US-Israel attacks?list 4 of 4Tehran hit by heavy bombing on day seven of US-Israel war on Iranend of listResearchers Mark Cancian and Chris Park said only a small amount of the estimated $3.7bn cost of the war in the first 100 hours – or $891.4m each day – was already budgeted for, while most of the costs – $3.5bn – were not.That meant the Pentagon would likely need to request more funding soon to cover the unbudgeted costs, they said, which was likely to prove a political challenge for the Trump administration and provide “a focal point for opposition to the war,” they said.Domestic cost-of-living concerns, inflation, and now a knock-on effect of rising gas prices due to the conflict are likely to further diminish support among US citizens for the war. It is also dividing Trump’s “America First” base, which he had promised in his presidential campaigns to not enter “foreign wars”.Noting that the US Department of Defense had released limited specifics on its operations, the researchers said their analysis drew on Congressional Budget Office (CBO) estimates of the operations and support costs for each unit, adjusting for inflation and unit size, and adding 10 percent for costs of “a higher operational tempo”.Their analysis said the US had expended more than 2,000 munitions of various types in the first 100 hours of the war, and estimated it would cost $3.1bn to replenish the munitions inventory on a like-for-like basis, with the costs increasing by $758.1m a day.Unbudgeted costs ‘substantial’United States Defense Secretary Pete Hegseth has said that the US bombardment on Iran is “about to surge dramatically”, entailing “more fighter squadrons … more defensive capabilities” and “more bomber pulses more frequently”.The report’s authors said that while air campaigns typically settled to a less frenetic pace after the intense early period of a conflict, “nevertheless, the unbudgeted costs here will be substantial”.They said this was unlike the recent US operations that led to the abduction of Venezuela’s Nicolas Maduro, where most costs were already in the budget.“That means that the [Department of Defense] will need additional funds at some point because the level of budget cuts needed to fund this conflict internally would likely be politically and operationally difficult,” said the report.It said the Trump administration might decide to ask for a supplemental appropriation to cover the war and any other unexpected expenses across the government, as the George W Bush administration had done at the beginning of the wars in Iraq and Afghanistan.“The political challenge for the administration will be that any funding action will become a focal point for opposition to the war,” it said.War costs ‘likely to shock’ CongressReporting from Washington, Al Jazeera’s Rosiland Jordan said the high cost of the war was “probably coming as a shock to members of Congress and the general public”.She said the Pentagon has reportedly put together a $50bn supplemental budget request in order to replace Tomahawk and Patriot missiles and THAAD interceptors already used in the first week of the war, along with other equipment that had been damaged or worn out so far.“The military burn rate has been rather high,” she said.Congress was already concerned about the budget deficit and the interest on the federal debt, she added.“Another $50bn request might give some legislators pause.”The human costThere has already been a huge human cost to the war.More than 1,332 people have been killed so far in Iran since the US and Israeli bombardment began on Saturday, according to the Iranian Red Crescent, with UNICEF saying at least 181 children are believed to be among the dead.In Lebanon, the death toll from Israeli attacks this week has risen to at least 123 people, the Lebanese Ministry of Public Health said, as a new wave of strikes pounded the country, in one of the fiercest fronts in the wider war.At least six US servicemen have died in the conflict, while 11 people in Israel have also died. There have also been nine deaths so far in Gulf Arab countries.