The war with Iran has cost the US some $37.5bn, so far - an increase of nearly $8bn since the last estimate in May, the self styled US "Secretary of War", Pete Hegseth, has said.
Hegseth told the Senate Appropriations Committee it was urgent that lawmakers approve another $87bn in congressional funding for the Pentagon, with $67bn of that destined for operations in the Middle East.
The hearing was disrupted several times by anti-war protesters and ended in a shouting match between the defence secretary and a senator.
It was Hegseth's first appearance on Capitol Hill since hostilities between the US and Iran restarted last week and comes after three American soldiers were confirmed killed in the region.
The White House asked Congress in April for $1.5tn for the Pentagon over the next fiscal year, which would raise American military spending to an all-time high in the modern era.
The US carried out an 11th consecutive day of strikes on Tuesday. Iran has been retaliating with strikes of its own against the US and its allies in the Middle East.
The defence secretary began Tuesday's testimony by saying, "we live in a dangerous world" and that it required bold and swift action.
After being interrupted by protesters, Hegseth went on to say his funding request came at an urgent time.
"Without these funds, we face critical shortfalls that threaten our ability to also simply pay our service members, rapidly replenish equipment and munitions, and sustain vital operations without disruption," Hegseth said.
Every dollar appropriated, he added, would be used to build the "lethality" of US military forces and "reinforce peace through strength".
Senate Appropriations Committee chairwoman Susan Collins, a Republican, questioned Hegseth over what the impact would be if the budget needs were not met.
Hegseth said current and future training for military members would need to be cut without the funds, as he repeatedly blamed former President Joe Biden's administration for what he said was an underfunded military.
The most senior Democrat on the committee, Patty Murray, pushed back on the funding request, saying it "does not make a lot of sense".
Asked by Democratic Senator Dick Durbin if he had an estimate for how much the war in Iran has cost so far, Hegseth gave the $37.5bn figure.
source: commonspace.eu with BBC (London) and agencies
