The U.S. defense industry is “not adequately prepared” for “a protracted conventional war” with an enemy such as China, according to a think tank study published Monday.

The Center for Strategic and International Studies (CSIS) ran a war games simulation that found that the U.S. would likely be depleted of some of its munitions, including long-range, precision-guided ones, in less than a week of war with China in the Taiwan Strait.

The U.S.’s use of weapons would exceed the Department of Defense’s stockpile, which would make sustaining a long-term war conflict “difficult,” especially as China is investing in munitions and other weapons systems five to six times faster than the U.S., according to the study.

The Russia-Ukraine war exposed the shortfalls of the U.S.’s defense industry, CSIS said, with the study finding that the nation’s inventories of some weapons, including Javelin anti-armor systems and Stinger anti-aircraft systems, are running low as the U.S. committed to sending more of these systems to Ukraine. The U.S. committed to sending more than 8,500 Javelin systems and more than 1,600 Stinger systems to Ukraine, leaving its own inventory low, according to the report.

The study said that the number of Javelin systems sent to Ukraine is about equal to the total number built for non-U.S. customers over the last 20 years. The study emphasized that the problem was not the U.S. assistance to Ukraine but the current incapacity of the defense industry to supply enough weapons for long-term conflicts.

“The main problem is that the U.S. defense industrial base — including the munitions industrial base — is not currently equipped to support a protracted conventional war,” the study stated.

The study also said that the U.S.’s foreign military sales (FMS) take too long because they need to be initiated by the Department of State and then executed by the Department of Defense and ultimately approved by Congress. Foreign sales have benefits, including supporting the U.S. defense industry, strengthening ally relations and preventing the sale of adversary systems to other countries, the study said.

“The U.S. FMS system is not optimal for today’s competitive environment — an environment where such countries as China are building significant military capabilities and increasingly looking to sell them overseas,” the study stated.

If the U.S. streamlined its FMS process by making it more efficient, the study said, it could “help establish predictable, efficient production rates” in the defense industry, which could help boost U.S. production levels.

“The bottom line is the defense industrial base, in my judgment, is not prepared for the security environment that now exists,” CSIS’s Seth Jones, author of the study, told The Wall Street Journal.

This study follows a separate one published by CSIS earlier this month that found if China invaded Taiwan, there would be “heavy” losses on all sides, including the U.S.

“How do you effectively deter if you don’t have sufficient stockpiles of the kinds of munitions you’re going to need for a China-Taiwan Strait kind of scenario?” Jones asked.