The US had spent more than $38 billion (€33 billion) on its war with Iran by the beginning of August, according to the country's Congressional Budget Office (CBO).
The estimate covers costs incurred by the US Department of Defence from the start of the conflict on 28 February to 1 August, just over five months later.
The Defence Department did not provide information to the CBO for its assessment, which instead relied on government databases and publicly available reports. The CBO said its estimates were therefore subject to “considerable uncertainty”.
Nevertheless, the figure broadly aligns with an estimate given by Defence Secretary Pete Hegseth in July, when he said the war had cost $37.5 billion.
The largest proportion of the cost is reportedly the $21.7 billion that has been spent on replacing munitions.
The CBO also warned about the depletion of missile-defence interceptors. It estimates the US has probably used between half and two-thirds of its inventory of those weapons since June 2025, leaving stocks depleted for several years.
On Monday, a Pentagon inspector general report warned that the US-led military campaign against Iran, known as Operation Epic Fury, had resulted in “strategic inventory shortfalls”.
The CBO also warned that the conflict is having a wider impact on the US economy, largely because disruption to oil and gas shipments through the Strait of Hormuz and Red Sea has pushed up energy costs.
The estimate was prepared in response to a request for information from Representative Brendan Boyle, the top Democrat on the House Budget committee.
Boyle criticised the amount spent: “this nonpartisan CBO report makes clear that the war has also cost American taxpayers tens of billions of dollars and counting, while continuing to drive up costs.”
“Donald Trump and Republicans have spent years telling Americans that we cannot afford to help families here at home,” Boyle said in a statement, "but apparently they can find tens of billions of dollars, and potentially much more, for a reckless war that is leaving Americans to pay the price.”
In June, the White House requested an additional $87.6 billion (€76 billion) in supplemental funding, much of it for the war effort. Congress has not approved the request.
