Washington, Sept. 16 -- The Iran war has cost the Pentagon about $38 billion in its first five months, with another $2- 3 billion expected to add up for each additional month of fighting, according to a new Congressional Budget Office (CBO) analysis.

The estimate, which covers costs through August 1, includes replacing weapons used in combat, equipment lost during operations, increased flight activity and higher fuel costs.

The monthly bill could vary depending on the intensity of the fighting. The CBO estimates that operations at the level seen in May and June cost about $2 billion a month, while the higher intensity recorded in July raised the monthly cost to roughly $3 billion.

The agency said the figure could rise further if military...