The United States needs more production lines making more missiles.

That’s the message from Congress to the Pentagon, via the Senate Committee on Armed Services’ recent markup of the 2020 defense budget. The markup contains a provision to continue the Pentagon’s work in acquiring high-end, long-range missiles in an effort to close what is known in the national security world as the “missile gap.”

As the Pentagon continues to reorient itself to counter threats posed by China, the Senate wants defense officials to maximize as many missile production lines as possible.

“There’s a huge missile gap between the United States and China in particular,” Rebecca Heinrichs, a senior fellow with the Hudson Institute who specializes in missile defense, told the Washington Examiner. “And so the United States has got to a point where we’re being prudent, and making sure that we have our own industrial base capable and ready to ramp up production rates.”

China has spent the last several years expanding its missile arsenal as part of what is known as an anti-access/area denial doctrine. Chinese leaders realized long ago that while they can’t compete with U.S. spending on things such as aircraft carriers and fighter jets, they can develop and acquire weapons to counter them at a fraction of the cost. Missiles, in particular, are good at preventing U.S. assets from entering China’s neighborhood.

While China has spent the last several years building up its missile arsenal, the U.S. has been depleting its stockpiles fighting the Islamic State and other terrorist groups through campaigns heavily reliant on airstrikes. Hellfire missiles and super-accurate Joint Direct Attack Munitions have been in particularly high demand and defense analysts are concerned current production might not meet future needs.

“So we look at what the inventory levels are that we need to be able to perform a mission under various war fighter scenarios,” said acting Deputy Secretary of Defense David Norquist during a talk at the Center for a New American Security on Thursday. “But you always … question, what’s the industry capable of producing if asked to ramp up?”

It’s difficult to put an exact number to the missile gap because of China’s “intentional ambiguity and unwillingness to enter arms control or other transparency agreements,” according a report by the Center for Strategic and International Studies. That said, the Senate markup makes specific reference to certain U.S. munitions, including the Long-Range Anti-Ship Missile, Joint Air-to-Surface Standoff Missile Extended Range, the MK-48 torpedo, and Harpoon missiles. All are used to destroy conventional military targets such as ships and buildings, another sign that Congress is eyeing future conflicts with adversaries like China and Russia.

But Heinrichs noted it is also important to focus on defensive capabilities like the Patriot missile defense system, which has been in high demand recently due to threats posed by North Korea and Iran. But the Patriot system is decades old and isn’t capable of intercepting the hypersonic missiles adversaries such as Russia say can evade U.S. defenses.

“[W]e’re not talking about trying to deter China in 10 years, we’re trying to get at it now, because we’re already behind,” said Heinrichs. “I think missile defense is one of the things that the American people intuitively understand and it empowers diplomacy … it gives us stronger deterrence because it makes the enemy think that perhaps it is not going to be able to get a successful attack off.”