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An Aug. 5 memo from Deputy Defense Secretary Steve Feinberg, first reported by The Washington Post, gives firms 21 days to submit plans to "drive significantly faster, more aggressive delivery schedules and/or increased production for critical capabilities."

"Years-long development cycles are not acceptable," Feinberg wrote, according to the Post. "We must dramatically accelerate our program schedules and expand our production capacity now."

Chief Pentagon spokesman Sean Parnell confirmed the memo's authenticity in a statement to USA TODAY, saying that "working directly with industry leaders to accelerate production is not new."

"From day one under Secretary Hegseth, this Department has been focused on delivering generational change to the speed, capacity, and lethality of America’s defense industrial base and the Arsenal of Freedom," Parnell said. "Deputy Secretary Feinberg is a generational leader in that effort, driving the hard work of fixing our broken, antiquated, and immensely complex acquisitions system so we can actually produce the weapons our warfighters need at the pace the threat demands."

Reuters, citing anonymous sources, reported Aug. 4 that the U.S. Army has used up much of its stockpile of long-range precision missiles during the five-month war with Iran. The missiles are mainly the Army's surface-to-surface weapons, known as Army Tactical Missile Systems and Precision Strike Missiles. Two sources told Reuters the conflict has consumed "virtually all" of those munitions.

The long-range munitions are designed to strike targets at extended ranges with precision.

Pentagon officials slammed the reported shortages as "false," and President Donald Trump claimed the United States had a "virtual unlimited supply" of missiles on Aug. 6.

A Center for Strategic and International Studies (CSIS) shortage analysis found that the United States has used about half of its Patriot interceptor, Precision Strike and Terminal High Altitude Area Defense missile inventories and a third of its Tomahawk long-range ground-attack missile inventory over the course of the war.

Experts said estimates of missile stockpiles are based on procurement figures in federal budget documents and public disclosures about the weapons' use in the war.

Mark F. Cancian, the lead author of the analysis, estimated the United States' remaining inventory could be seriously exhausted if the war drags on for several more months.

"For a war against Iran, we could continue that for some time, for months," Cancian previously told USA TODAY. "But my suspicion is the Joint Chiefs of Staff sees us at a danger point for conflict with China, where we’d need all these missiles, and that’s why we’d call this a window of vulnerability."

Refilling the U.S. missile stockpiles will take years because of manufacturing constraints, a handful of experts said.

The nation will not be back at prewar defense missile levels until the middle of 2029 and at prewar Tomahawk missile levels until 2030 or 2031, according to the CSIS analysis.

"This really has long-term strategic implications for the United States," Kelly A. Grieco, a senior fellow at the Stimson Center, previously told USA TODAY. The center is a think tank focused on global peace issues. "It’s going to take years to get back up to the levels we had before we started this war, and that prewar level was already too low."

There are many reasons for the shortage in munitions, USA TODAY previously reported.

Among them, the missiles are difficult to manufacture, supply chain squeezes can interrupt production, and missile production decisions are also made years in advance.

Another factor in defense systems, including Patriot missiles, is that typically two to three interceptor missiles are fired at every attack missile. Iran is estimated to have fired well over 1,000 attack missiles over the course of the war.

Experts said years of U.S. military operations have also contributed to declining inventories.

The missiles expended include hundreds of defensive interceptors used against Houthi attacks in the Red Sea, as well as offensive missiles used in operations against Iran, during the raid that captured Venezuelan President Nicolás Maduro and in strikes against ISIS in Nigeria, according to CSIS estimates.

U.S. missile shortages are already becoming a factor in Ukraine’s war against Russia, experts previously told USA TODAY. Ukraine is one of several American allies that rely on U.S.-made systems for defense.

Other allies that could be impacted by the shortage include Japan and Taiwan, as well as the Gulf states currently fighting off Iranian attacks, experts said.

Specific inventory numbers are classified, but CSIS estimates that about 65% of Patriot interceptors were expended between February and July, with less than 850 left on hand, down from 2,330 before the Iran war began.

"If the fighting starts up again and the Iranians keep firing missiles at the Gulf states then they’ll be screaming for additional missiles," Cancian said.