South Korea will speed up building its own missile defense aimed at low-flying targets, while seeking ways to develop “multi-layered” deterrence against North Korea, the defense ministry said Tuesday.

Seoul has been gradually building an independent, low-tier missile shield called the Korea Air and Missile Defense, with mid-term plans to acquire the latest Patriot missiles and long-range early warning radars.

In addition to the terminal phase system, the defense ministry said it is considering multi-layered defense to effectively strike ballistic missiles coming from different altitudes.

“Our military is establishing a low-tier terminal-phase KAMD considering the range of North Korea’s incoming ballistic missiles.

It was reflected in the military acquisition plan and will be completed faster than expected,” ministry spokesman Kim Min-seok said in a briefing. “Our military is also looking into various measures to bolster the terminal phase, low-altitude defense to effectively counter North Korea’s nuclear and missile threat.”

Kim didn’t specify weapons systems, but he excluded the Standard Missile-3, which intercepts missiles at an altitude over 400-500 kilometers, from the shopping list.

Although there have been calls to adopt the long-range missile defense to establish a multi-layered shield against the North, Seoul’s defense ministry has remained cautious over the American missile program as it could spur a regional arms race involving China and further contribute to mounting costs in the national missile program.

Kim’s remark raised speculation that Seoul is seeking to adopt systems like the Terminal High Altitude Area Defense by Lockheed Martin as a possible next step. THAAD is designed to shoot down short, medium and intermediate ballistic missiles in their terminal phase, using a hit-to-kill method.

South Korea plans to upgrade PAC-2 missiles imported from Germany to PAC-3 by Lockheed Martin as skepticism has risen over the old interceptor’s capability to thwart North Korea’s ballistic missiles, which might be tipped with chemical or nuclear warheads.

The latest move comes as South Korea is scheduled to take over the wartime operational command of all troops on the peninsula in December 2015, a timeline that had already been pushed back from the previous deadline of 2012.

In light of Pyongyang’s nuclear test and warlike rhetoric in the spring, Seoul asked Washington to delay the schedule to buy more time to beef up its military. The two nations have agreed to reset the appropriate timing next year.

It also comes at a time as Seoul is under pressure to play a bigger role in the U.S. initiative to beef up its regional missile defense along with Japan as part of its rebalancing toward Asia.

In response to Seoul’s move to delay the 2015 transition deadline, lawmakers demanded the military lay out a blueprint plan to bolster its missile defense for budget deliberations, the key deterrence capability against North Korea’s nuclear and missile program.

Defense Minister Kim Kwan-jin also said the South Korean military is speeding up efforts to establish the KAMD, while reviewing other options to bolster the missile shield.

“In addition to upgrading (the current system) to the PAC-3 system, we will review other measures for multi-layered defense,”

Kim said during a parliamentary audit on Monday. “For the multi-layered defense, long-range and mid-range surface-to-air missiles as well as other systems will be considered.”

Seoul has been pushing to bolster its defense against the communist rival after it successfully fired off a long-range rocket last December. Pyongyang claims the launch was aimed at putting a satellite into orbit, but Seoul and Washington consider it as a covert ballistic-missile technology test.

When the North threatened to strike South Korea and U.S. Pacific islands and placed its medium-range missiles on its east coast in April, the Pentagon stationed missile interceptors in Alaska and moved Aegis guided-missile destroyers and THAAD to Guam.

Japan deployed its PAC-3 batteries in Tokyo.

During a bilateral defense summit earlier this month, U.S. Secretary Chuck Hagel pledged to cooperate with Seoul to bolster interoperability of the alliances command and control system for missile defense against North Korea.

“We’re working with the Republic of Korea on their missile defense system. These don’t have to be identical as long as they are interoperable,” he said. “We want systems that work together and that are interoperable. It involves a lot of command and control, which is complicated.”

Military experts say operating missile defense at different altitudes could provide enhanced protection against North Korea’s mid- and long-range ballistic missiles.

“THAAD has a large footprint, and the Patriot ... protects a smaller area. Usually THAAD and Patriot are deployed together because they provide in-depth tier and layered defense capability.”

Orville Prins, the vice president of business development for air and missile defense at Lockheed Martin, told Yonhap News Agency last month.

South Korea’s procurement agency and Air Force officials showed interest in a long-range surface-to-air system during their visit to the U.S. in April and that discussions are currently under way on whether to acquire THAAD or develop an indigenous program that fits the role, Prins said.

In July, the defense ministry submitted a 214.5 trillion won

($192.6 billion) budget request for the 2014-2018 fiscal year to the parliament for deliberation, with 70.2 trillion won assigned for acquisition of interceptors, satellites and high-altitude spy drones. (Yonhap News)