The Pentagon has used at least 45% of its stockpile of Precision Strike Missiles; 50% of its Terminal High Altitude Area Defense (THAAD) interceptors inventory; and almost half of its stockpile of Patriot ballistic interceptor missiles—all within the first seven weeks of war with Iran, according to an analysis published this week by the Center for Strategic and International Studies (CSIS).

Though the U.S. has enough missiles to continue to fight in the Iran war without limitations, there is an increased risk of the U.S. military being insufficiently prepared for a future war in the Pacific, noted the report, authored by Mark Cancian, a retired U.S. Marine Corps colonel, and Chris Park, a CSIS research associate. Prior to the conflict in Iran, munitions stockpiles were already drained. CSIS estimated it would take one to four years to restock the seven major munitions to prewar levels.

“The diminished munitions stockpiles have created a near-term risk,” the report said. “A war against a capable peer competitor like China will consume munitions at greater rates than in this war. Prewar inventories were already insufficient; the levels today will constrain U.S. operations should a future conflict arise.”

Ballooning defense spending

In the past two months, the U.S. has brokered deals with defense firms to bolster its munitions, including Honeywell Aerospace, which will “surge production of critical ​components for America’s munitions stockpile” following a $500 million multiyear investment, according to the Pentagon. President Donald Trump has requested a $1.5 trillion defense budget for fiscal 2027, which the Pentagon described as the largest year-over-year jump in defense spending since World War II.

Using data from the CSIS report, Fortune calculated the U.S. has so far spent about $24 billion on the seven major munitions used, but the cost of the Iran war is projected to far exceed that sum. Public policy expert and Harvard Kennedy School lecturer Linda Bilmes said the cost of the war is likely to exceed $1 trillion, as the administration underestimates the short-term costs of infrastructure damage, as well as long-term costs, such as lifetime disability benefits for thousands of veterans.

Data from the analysis runs counter to the narrative of President Donald Trump, who said at the beginning of the conflict the medium- and upper-medium-grade munitions stockpiles have “never been higher or better” and the U.S. has a “virtually unlimited supply” of these weapons.

Chief Pentagon spokesperson Sean Parnell told Fortune in a statement the military “has everything it needs to execute at the time and place of the President’s choosing.”

“Since President Trump took office, we have executed multiple successful operations across combatant commands while ensuring the U.S. military possesses a deep arsenal of capabilities to protect our people and our interests,” he said.

Munition spending concerns

Of concern to experts like Bilmes is the U.S.’s disproportional spending on munitions compared with Iran. Iran’s Shahed drones each cost between $20,000 and $50,000 to produce, per Reuters, while a Patriot interceptor used to shoot down drones or more complex aerial threats could cost about $4 million, as it requires more sophisticated technology to function.

“Not only are the costs high, but we have these in this imbalanced situation where costs are disproportionately high compared to the cost of producing drones,” Bilmes told Fortune.

The Patriot is a particularly sought-after missile, with 18 other countries using it in addition to the U.S., which has given 600 of them to Ukraine and other allies over the course of the war. Though Lockheed Martin expects to increase production of the PAC-3 MSE to 2,000 annually by 2030, CSIS analysts said the U.S. will have to be more judicious in how it allocates its current supply of the missiles, as well as its annual deliveries, which it currently puts at 600 a year. While some strategists have advocated for the U.S. stockpiling Patriot missiles in case of a war with China, Ukraine has also requested additional munitions from the U.S., the CSIS analysis noted. That’s in addition to other U.S. allies similarly seeking the missiles.

According to CSIS, the Pentagon may have alternative air-to-air missiles, including the AIM-120, but they are similarly expensive at $1 million. The U.S. and Gulf states have resorted to using helicopters and fixed-wing aircraft with guns as a solution to limited inexpensive interceptors. The limited resources have left some U.S. officials worrying about how the U.S. will continue supplying itself with munitions.

“The Iranians do have the ability to make a lot of Shahed drones, ballistic missiles, medium-range, short-range, and they’ve got a huge stockpile,” Arizona Democratic Sen. Mark Kelly told CNN last month. “So at some point … this becomes a math problem, and how can we resupply air defense munitions? Where are they going to come from?”