The US already spent more than $11.3bn in first six days of conflict, but price tag does not include all spending

Pentagon officials told top lawmakers in a closed-door briefing on Tuesday that the cost of the war against Iran has already exceeded $11.3bn in its first six days, but the true cost of the opening days of the conflict is likely far greater, according to two people familiar with the matter.

This figure, first reported by the New York Times and confirmed by the Associated Press, in addition to the Guardian, represents the most detailed cost assessment that Congress has received so far as lawmakers seek clarity about the scope and duration of the conflict.

But the estimate, presented during a classified briefing on Capitol Hill, appeared largely limited to munitions expenditures and does not capture the full cost of the opening days of the conflict, one person familiar with the matter told the Guardian. Additional costs to consider include the deployment of forces to the region, medical expenses and the replacement of military aircraft lost in war.

The Guardian reported last week that the US spent about $2bn each day in munitions at the beginning of the conflict before spending fell to $1bn each day. The cost per day is expected to fall further as the war continues, unless the situation escalates.