The United States military has spent more than $47 billion so far prosecuting the war in Iran, according to Pentagon data obtained by Reuters, a figure more than a quarter higher than the Defence Department estimated in July. The Pentagon has not published the estimate and did not immediately respond to Reuters' request for comment.

More than $29 billion of the total is the projected cost of replacing expended munitions, Reuters reported, with more than $6 billion more needed to replace military equipment and so-called platform losses, including aircraft and many drones lost during the fighting. President Donald Trump launched the war jointly with Israel in February, predicting it would last a short time.

Why the bill keeps rising

The early strategy relied on expensive precision missiles to strike Iranian defences before cheaper munitions could be used, Reuters reported. An April ceasefire then gave Iran time to dig out underground storage facilities and bring back online defences, missiles and drones that had been inaccessible. Trump has since imposed a naval blockade on Iran to cut off its oil export revenue and has held out the possibility of restarting combat operations after the midterm elections, with US officials saying the Pentagon has been planning for a resumption of heavy fighting if ordered.

The rising cost lands as Republicans face the political fallout of an unpopular conflict ahead of the 3 November election that will decide control of Congress, with the war's effect on energy costs weighing on support for Republican candidates and on Trump's approval ratings. Sources: Reuters.