Washington: The first week of the war against Iran has cost the United States more than $11.3 billion, lawmakers were told during a Pentagon briefing, according to a report by The New York Times that highlights the rapid pace at which the conflict is consuming weapons and resources.

The newspaper, citing unnamed sources familiar with Tuesday’s closed-door briefing at the Pentagon, reported that members of Congress were informed the figure does not include several expenses linked to the military buildup ahead of the strikes, indicating that the total cost for the opening week could climb significantly.

Defence officials had earlier told Congress that about $5.6 billion worth of munitions were used in just the first two days of fighting, US media reported, pointing to a burn rate far exceeding earlier public estimates.

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Meanwhile, the Washington-based think tank Centre for Strategic and International Studies (CSIS) estimated that the first 100 hours of Operation Epic Fury cost $3.7 billion, or more than $891 million per day.

CSIS noted that most of those expenses, about $3.5 billion, had not been previously budgeted.

The Iran War Cost Tracker website, which estimates the conflict’s expenses in real time, showed the total spending had crossed $17 billion by around 08:00 GMT on Thursday.

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According to the site, the United States is currently spending roughly $1 billion per day on the war.

However, it cautioned that the actual cost could be significantly higher as the estimates do not include long-term expenditures such as healthcare for military veterans.

Meanwhile, the price of Brent crude oil, the international standard, spiked back over $100 as Iranian strikes hit ships in the region's waters and the ongoing American-Israeli war with Iran showed so signs of slowing.

Thursday’s major developments include Iranian attacks against commercial ships around the Strait of Hormuz and Iraq's port of Basra, escalating a campaign of squeezing the oil-rich Gulf region as global energy concerns mount. The U.S. campaign of airstrikes in Iran is now in its 13th day.

The Israeli military is also striking Iran and its militant ally Hezbollah in Lebanon, where more than 800,000 people have been displaced by the fighting.