The global supply crisis of Patriot missiles is exacerbated by extensive use in the Gulf

(CNN) - The global supply crisis of Patriot interceptor missiles worsened as a result of their extensive use in the Gulf region during March and April, often to counter attacks by relatively low-cost Iranian drones.

US weapons stockpiles, including vital missiles for air defense, remain in severe shortage following the significant escalation in the war with Iran in recent weeks, according to three sources familiar with recent Pentagon data and a new report by independent analysts.

In a report issued by the Center for Strategic and International Studies (CSIS), researchers estimated that US stockpiles currently contain fewer than 827 Patriot interceptors, and fewer than 278 THAAD ballistic missile interceptors.

These numbers reflect a significant depletion of the stock that was available before the war, as the center estimated that stock at about 2,200 Patriot missiles from the two latest models of the system, and 452 THAAD missiles.

These systems are the US Army's main means of intercepting and destroying incoming enemy ballistic missiles, while the cost of one interceptor missile amounts to millions of dollars.