The military is hoping to buy SM-3 interceptor missiles for Aegis ships that could destroy North Korean ballistic missiles at an altitude of 150 km.
But the plan is risky since the SM-3 missiles constitute the core of the U.S.-led missile defense program, which Seoul has not so far joined because China is extremely wary of it.
Defense Minister Kim Kwan-jin told a National Assembly audit on Monday that he would "research and consider multi-level defense measures" involving interceptor missiles. The Defense Ministry also told Yoo Seung-min at the National Assembly's Defense Committee that "complementary operation" of existing missiles and the SM-3 missiles could "boost" South Korea's missile defense.
A senior ministry official told the Chosun Ilbo that the military is "considering whether the SM-3 is necessary for the Korean air missile defense system."
Until now, the military has denied it is even thinking about acquiring the SM-3 missile system because it did not want to give the impression that it was joining the U.S.-led missile defense program by the back door.
This is the first time the defense minister has officially commented on the possibility.
South Korea's own missile defense consists of ground-based Patriot or PAC-2 and improved PAC-3 missiles, which are capable of intercepting North Korean ballistic missiles at low altitudes of 10 to 15 km.
They also have a high failure rate because the low altitude leaves only 5 to 7 seconds to intercept incoming missiles.
Beijing is almost certain to protest if Seoul buys the SM3s, but it needs some kind of more effective missile defense.
U.S. Defense Secretary Chuck Hagel said in bilateral defense talks last week that missile defense is the most important capacity for the South Korean military if it is to regain full troop control.