The United States should shore up its defenses against the growing threat of conventionally armed ballistic and cruise missiles, the head of a Washington, D.C., think-tank said Oct. 11.

U.S. missile defense programs are currently focused on using large, expensive interceptors to destroy small numbers of nuclear-armed ballistic missiles, such as those that could be fired by North Korea. But American and allied bases in East Asia and elsewhere are increasingly vulnerable to massive volleys of conventional, precision-guided weapons that could be launched by potential adversaries, such as China, said Thomas Mahnken, president and chief executive officer of the Center for Strategic and Budgetary Assessments (CSBA).

Defeating such salvos will require new weapon systems that have deep magazines and operate at a relatively low cost per shot, Mahnken said at a Stimson Center event on the U.S.-Japan alliance. Such systems could include lasers, high-power microwaves, and gun-launched or high-speed projectiles.

“That will call for a very different approach to air and missile defense,” said Mahnken, a former deputy assistant secretary of defense for policy planning. “Whether it’s directed energy, railgun or hypervelocity projectile, we have to have new concepts for defending those facilities and assets.”

Such defensive systems are in development but are years away from being ready to protect American and allied forces.

According to a report that CSBA released in May, conventional guided weapons fielded by China and Iran pose an especially significant challenge to the U.S. military’s ability to operate. China has deployed sophisticated anti-ship and land-attack cruise missiles and multiple types of ballistic missiles. Iran is seeking to obtain improved guidance systems from North Korea, China and others to allow its weapons to hit small fixed targets or moving targets such as ships.

“Since the end of the Cold War, the Pentagon had the luxury of assuming that air and missile attacks on its bases and forces would either not occur or would be within the capacity of the limited defenses it has fielded,” the report says. “These assumptions are no longer valid, given that America’s adversaries have taken advantage of proliferating guidance and missile technologies to create their own precision strike capabilities. Salvos of guided weapons launched during future engagements could overwhelm the defenses of U.S. forces, reducing America’s ability to project power.”