South Korean Defense Minister Kim Kwan-jin on Wednesday brushed aside the possibility of joining the U.S.-led regional missile defense, putting emphasis on the indigenous program aimed at intercepting low-flying missiles coming from North Korea.

During a parliamentary audit on Monday, Kim said the South Korean military is speeding up establishing the Korea Air and Missile Defense (KAMD). He added that it is also considering bolstering the system with other longer-range interceptors to ward off North Korea's nuclear and missile threat.

Kim made the remark as the lawmakers demanded the military to lay out a blueprint to bolstering its missile defense for budget deliberations. The demand was in response to the move to delay the 2015 deadline for the transition of wartime operational control(OPCON) to Seoul from Washington, amid the growing nuclear threat from Pyongyang.

His remark had fueled media speculation that a deal might have been reached during a bilateral defense summit earlier this month that South Korea would join the U.S. missile shield in return for a possible delay in OPCON transfer.

The two sides agreed to revisit the OPCON matter and decide on the postponement early next year.

On Wednesday, the South Korean defense chief made clear that Seoul is not considering joining the U.S. missile program.

"Because the KAMD is aimed at destroying North Korea's missiles, its target and interception range are different from those of (the American missile defense)," Kim told reporters at the defense ministry. "We have to consider the short missile range on the Korean Peninsula and the enormous price. It is doubtful whether the military would draw support for the plan even if those conditions are met."

Kim said the military has already approved the budget plan to upgrade the PAC-2 to PAC-3 and plans to develop mid- and long-range surface-to-air missiles, while cooperating with the U.S. forces to share intelligence assets to detect the North's missile and nuclear activities.

"Under the South Korea-U.S. joint deterrence posture, we can share the American weapons system to detect and track North Korean missiles, which is very useful," Kim said. "But there was no request from the U.S. for Seoul to join its missile defense system, and U.S. officials acknowledged the difference between the KAMD and the American missile system."

During the high-profile defense summit in Seoul, U.S. Defense Secretary Chuck Hagel pledged to cooperate with Seoul to bolster "interoperability" of the allied command and control system for missile defense against North Korea.

The push for multitiered defense raised speculation that Seoul is seeking to adopt systems like the Terminal High Altitude Area Defense (THAAD) 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.

Kim said the military is not currently considering purchase of THAAD and SM-3 missiles for Aegis destroyers, saying that they are not currently fit for security situations on the peninsula considering the value for its enormous cost.

While the American shield intercepts missiles from boost, ascent to terminal stage, the KAMD focuses on striking missiles at the terminal stage at different altitudes, Kim said.

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 raise defense costs. (Yonhap News)