The United States' war in Iran has cost $25 billion so far, a senior Pentagon official said on Wednesday, providing the first official estimate of the military's price tag for the conflict.

With just six months before the mid-term elections in which Trump's Republicans may face an uphill battle to keep their House majority, Democrats are riding high in public opinion polls as they attempt to link the unpopular Iran war with affordability.

U.S. Defence Secretary Pete Hegseth sought to defend the Iran war in fiery remarks to Congress, saying it was not a quagmire and attacking Democratic lawmakers as "feckless" for criticising the unpopular conflict.

"You call it a quagmire, handing propaganda to our enemies? Shame on you for that statement," Hegseth said before the House Armed Services Committee, slamming "reckless, feckless, and defeatist" Congressional Democrats

Jules Hurst, who is performing the duties of the comptroller, told lawmakers on the House Armed Services Committee that most of that money was for munitions.

Hurst did not detail what that cost estimate included and whether it took into account the projected costs of rebuilding and repairing base infrastructure in the Middle East damaged in the conflict.

Rep. Adam Smith, the top Democrat on the House Armed Services Committee, responded to Hurst: "I'm glad you answered that question. Because we've been asking for a hell of a long time, and no one's given us the number."

The United States started carrying out strikes against Iran on Feb.28 and the two sides are currently maintaining a fragile ceasefire. The Pentagon has poured tens of thousands of additional forces into the Middle East, including keeping three aircraft carriers in the region.

Thirteen U.S. troops have been killed in the conflict and hundreds wounded.

Disruptions in shipments of oil and natural gas since the war started have caused a run-up in U.S. gasoline prices and agricultural products such as fertilizers, on top of the long list of other high consumer prices.

Trump's popularity has taken a beating ​since the U.S. and Israel launched a war against Iran on February 28 that has led to a surge in gasoline prices.

Just 34% of Americans approve of the U.S. conflict with Iran, down from 36% in mid-April and 38% in mid-March, a recent Reuters/Ipsos poll ⁠found.