WASHINGTON (AP) — U.S. military contractors need at least three years to replenish stockpiles of three key weapons systems used heavily in the Iran war, according to an analysis released Wednesday, adding to concerns that American forces would have limited firepower in any future conflict with China.

The weapons systems are Tomahawk cruise missiles, which are used to strike targets deep inside enemy territory, and Patriot and THAAD interceptors that defend against incoming missiles and drones.

“The United States has enough munitions for any plausible scenario in the Iran war, but the depleted inventories have created a window of vulnerability for a potential Western Pacific conflict,” the Center for Strategic and International Studies said in its new report, provided to The Associated Press. “The time needed to rebuild those inventories has thus become a major concern.”

China has a stated goal of ensuring its military is capable of taking Taiwan by force if necessary by 2027, which experts see as more aspirational than a hard deadline. But Chinese President Xi Jinping warned this month that if Washington mishandles its relations with the self-governing island, the U.S. and China could end up clashing or even in open conflict.

Trump administration is boosting funding, but production takes time
The analysis by the Washington think tank factors in the Republican Trump administration’s historic defense budget proposal of $1.5 trillion for 2027, which significantly accelerates spending on high-end munitions that began during the Democratic Biden administration. While there’s bipartisan agreement in Congress to boost inventories, “the problem today isn’t money; it’s time,” the report said.

“It takes time to expand production capacity and to build these complex systems,” the report said, adding that the window of vulnerability will last “for several years until inventories return to their previous levels and another several years before they get to the levels that war planners desire.”

Although munitions inventories are classified, CSIS said sufficient public information exists in Pentagon budget materials to estimate production timelines.

President Donald Trump and Defense Secretary Pete Hegseth have insisted the U.S. is capable of fighting any war. They have pushed defense contractors to speed up munitions production, with Hegseth telling lawmakers last month that military spending under Trump will help manufacturers double or even triple their capacities.

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

“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,” Parnell said.

Some military experts have pushed back. Pentagon officials “knew the reality of our military stockpiles and hopefully told someone, ‘Hey, if we go to this fight, even in the most conservative estimates, we are drawing down our stockpiles to a critical level,’” said Virginia Burger, a senior defense policy analyst at the Project On Government Oversight watchdog group and a former Marine officer.

Concerns about diminished stockpiles were a theme at recent congressional hearings. For Democrats, the munitions supply is a damning metric against the Iran war, which Trump launched without lawmakers’ approval. Some Republicans argue that the problem stems from the U.S. sending Patriot missile defense systems to Ukraine after Russia invaded in 2022, although several American allies use those systems.

The roots of the predicament can be traced to the end of the Cold War, said Mark Cancian, a retired Marine colonel and senior adviser at CSIS who co-authored the study with research associate Chris H. Park.

After the fall of the Soviet Union in late 1991, the U.S. assumed future wars would be short and regional with little need for large numbers of such high-end weapons, Cancian said in an interview. The Pentagon ordered relatively low numbers, assuming the military would not need many of them. Military contractors responded in kind, relying on a relatively small manufacturing footprint to build them.

Russia’s war with Ukraine showed that wars could be protracted and require deep inventories of advanced weapons, Cancian said. At the same time, U.S. military strategists were war-gaming possible conflicts in the western Pacific.

“The thinking started to change, but it just takes time to build inventories,” Cancian said, adding that part of the challenge is bringing up to speed a complicated web of supply chains and subcontractors that produce very novel components.

President Joe Biden’s administration should get some credit for starting conversations with the defense industry, putting money into the industrial base and ramping up production, said Cancian, who oversaw acquisitions of military hardware at the Office of Management and Budget under Presidents George W. Bush, a Republican, and Barack Obama, a Democrat.

“A lot of people in the Trump administration are inclined to say that everything was terrible until they arrived, and that’s not true,” Cancian said. “Now, it is true that the Trump administration really increased funding.”

How long it will take to rebuild key stockpiles
The U.S. fired 1,000-plus Tomahawk missiles at Iran, and it could take until late 2030 to fully replenish the prewar inventory, CSIS estimates show.

Fewer than 200 Tomahawks are made a year because of small orders in the past, the report says. However, manufacturer Raytheon has a goal of ramping up capacity to more than 1,000 per year.

RTX, Raytheon’s parent company, declined to comment on the CSIS findings because it had not yet seen the report. But RTX pointed to investments of several billion dollars to boost production, including expanding facilities in Alabama and Arizona.

For in-demand air defense systems, replacing as many as 290 THAAD, or Terminal High Altitude Area Defense, interceptors that shot down incoming Iranian drones and missiles could take until the end of 2029, CSIS estimates. Replenishing more than 1,000 Patriot interceptors should wrap up in mid-2029.

Lockheed Martin is significantly boosting production of rounds for both systems, while deliveries of THAADs “were apparently re-sequenced to prioritize U.S. needs over those of allies and partners,” CSIS noted.

“Patriot deliveries pose a dilemma for the United States because of the need to replenish its own inventories, help Ukraine defend against Russian missile attacks, and meet the needs of 17 other countries that use the interceptor,” the report said.

Lockheed Martin said in a statement that it’s investing $9 billion through 2030 and “is already delivering tangible results to meet heightened munitions demand, including a new facility in Alabama announced last week along with more than 20 others across the United States.”

In the meantime, CSIS said a potential conflict with China is “not all bleak,” with the U.S. military recently displaying its capabilities against Iran, Venezuela and the Houthi rebels in Yemen.

“China is deeply aware that it has no recent combat experience and that it performed poorly in its last war — against Vietnam in 1979,” the report said. “That difference in experience may preserve deterrence until munitions inventories are restored.”