The US military's Operation Epic Fury against Iran has already imposed a staggering financial burden on American taxpayers, with the first 100 hours of the campaign costing an estimated $3.7 billion, or $891.4 million per day, according to a US defense think tank.

Of the $3.7 billion, $3.5 billion – more than 94% – is not budgeted, said the Center for Strategic and International Studies (CSIS) in an analysis last week.

The unbudgeted costs alone could force the Pentagon to seek additional funding, shifting more of the burden to taxpayers, the CSIS analysis warned, as US President Donald Trump and Defense Secretary Pete Hegseth signaled that the conflict could drag on for weeks.

The CSIS analysis breaks down the operation's costs into three key categories:

–– operational costs (approximately $196 million total, with $178 million budgeted and the rest unbudgeted);

–– munitions replacement (approximately $3.1 billion), none of which is currently budgeted;

–– and replacing combat losses and repairing infrastructure damage (approximately $350 million), also unbudgeted.

The CSIS analysis emphasized that future costs will hinge largely on the intensity of the operation and the effectiveness of Iranian retaliation.

The Pentagon will likely need to secure additional funding to cover the unbudgeted costs, as "the level of budget cuts needed to fund this conflict internally would likely be politically and operationally difficult," it said.

CSIS said its analysis comes as members of Congress, the media, and the public in the United States are increasingly questioning the financial toll of the Iran campaign.

The think tank noted that its estimates are based on limited details released by the Pentagon, which has provided fewer specifics about Operation Epic Fury than in previous Middle East campaigns.

Total cost could be 'astronomical'

With no end in sight to the Middle East crisis, US economic forecasters are also beginning to tally the potential cost – and their estimates range from tens of billions to "astronomical" sums that could rival the nearly $3 trillion price tag of the Iraq War.

Kent Smetters, faculty director of the Penn Wharton Budget Model, a research-based initiative housed at the University of Pennsylvania, estimated in an interview with CNN that a two-month conflict could cost between $40 billion and $95 billion.

The final figure, he explained, would depend on whether the US deploys ground troops and how quickly munitions are replenished.

Lindsay Koshgarian, program director of the National Priorities Project at the Institute for Policy Studies, described the conflict as "highly unpredictable," noting that its full cost will not be known until it is over.

She told CNN that the war is "not necessary" and diverts resources from policies that could "make life more affordable for Americans."

Drawing a historical parallel, Koshgarian pointed out that the Iraq War ultimately cost nearly $3 trillion. "So this could be astronomical, easily," she warned.