The U.S. Army has reportedly exhausted much of its stockpile of precision long-range missiles during the five months the U.S. has been at war with Iran.

The depleted stockpiles are raising concerns about the U.S. military's readiness for future conflicts, Reuters reported, citing unnamed sources. 

The missiles, known as Army Tactical Missile Systems (ATACMS) and Precision Strike Missiles (PrSM), are the Army's primary surface-to-air weapons. "Virtually all" of these missiles have been used up, the sources told Reuters. 

The missiles cost more than $1 million each and are a key part of the U.S. military's arsenal, as they allow strikes from a safe distance. Without the missiles, President Donald Trump may have to rely on higher-risk piloted bombing missions should large-scale attacks on Iran resume.