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The Pentagon told Congress the US war with Iran had cost $43.6 billion as of September 3, with another $1.5 billion set aside for fuel needs.
The total of $45.1 billion is higher than the Pentagon’s July estimate of $37.5 billion and the CBO’s $38 billion projection through August 1.
The figure does not include installation repairs or wider operational expenses
The US war with Iran has cost $45.1bn, higher than both the Pentagon’s July estimate and the Congressional Budget Office’s projection through August 1. The Pentagon informed Congress on Friday that the conflict had cost $43.6bn as of September 3, with another $1.5bn set aside for supplementary fuel needs, according to a CNN report.
That total does not include installation repairs and wider operational expenses. It also exceeds the CBO’s $38bn estimate for the war through August 1 and the Pentagon’s own $37.5bn estimate released in July.
It also comes as the CBO warns that the conflict is adding to inflation pressures, lifting energy costs and pushing Treasury yields higher.
CBO Cost Estimate
The CBO put the war’s cost at about $38bn as of August 1 in a report dated September 15, 2026. It said that figure covered the Department of Defense’s operational, logistical and sustainment costs tied to the conflict with Iran.
That estimate included replacing expended munitions and equipment lost in battle, increased flying hours, other operations and higher fuel costs. The office wrote that the tally reflected "that the initial, intense phase of the conflict lasted just over a month (less intense combat operations are still ongoing) and that relatively few US forces have been involved compared with the much larger and longer US operations in Iraq and Afghanistan."
The CBO excluded some items. It did not include costs borne by other parts of the federal government, such as increased fuel costs for the Postal Service. It also left out costs already built into the federal budget, including the basic operating costs of the military forces involved.
Future Cost
The CBO told Congress that spending would increase slowly if violence stayed low and sporadic, as it did in May and June, and rise rapidly if the conflict intensified again, as it did in July.
It estimated the war would keep costing the US about $2bn to $3bn a month after August 1. "Monthly costs could be higher still if the violence escalated further," it added.
Inflation And Rates
The CBO told Congress the war is expected to increase inflation in the first quarter of 2027, raising costs at a time Americans are growing more concerned about the economy.
The office said the main economic effect comes from inflationary pressure caused by reduced shipments of oil and natural gas through the Strait of Hormuz and disruptions to shipping through the Red Sea. That reduction has raised energy prices globally. "In CBO’s assessment, the effects of those higher energy prices will put upward pressure on consumer prices," the report added.
The CBO estimated that, in the first quarter of 2027, inflation measured by the personal consumption expenditures, or PCE, price index would be 0.5 percentage points higher than it projected in February 2026, and core PCE inflation is now seen 0.3 percentage points higher than previously projected. It also estimated that conflict-driven inflation would lift interest rates on Treasury securities, with rates on 3-month Treasury bills nearly 0.2 percentage points higher in 2026 than the agency estimated this past.
