Some estimates show the U.S. has used more than half of its stockpiles for some weapons systems in the war with Iran.

The Center for Strategic and International Studies found the U.S. has enough missiles to continue fighting in Iran under any plausible scenario, but the group says the true issue with the shrinking stockpiles is future wars.

"We can go on against Iran for quite a long time, even if we've used half the inventory, that means that half the inventories are still available," said retired U.S. Marines Colonel and senior adviser with the CSIS Defense and Security Department Mark Cancian.

"The risk is about a future conflict in the Western Pacific against China."

Cancian points to reports that military officials have grown more concerned over the U.S. weapons inventory when factoring in other possible conflicts, such as one with China.

"The depletion of munitions was a major topic and a major reason for the suspension of air attacks," Cancian said.

"Our inventories were getting way below what the war planners wanted, that might encourage China to do something."

Almost one-third of Tomahawk missiles have been used since the war in Iran began. Nearly two-thirds of patriot missile interceptors have been depleted.

Just over half of precision strike missiles remain. President Donald Trump insists the U.S. has plenty of munitions to continue in Iran.