The nominee for the chairman of the Joint Chiefs of Staff (JCS) vowed Friday to speed up major weapons programs to bolster defense capabilities, saying North Korea's missile and nuclear ambitions are posing the greatest threat to South Korean national security.

President Park Geun-hye last month appointed Adm. Choi Yun-hee to the JCS chief, marking the first time that a Navy chief has been appointed to the top commander post. His appointment is subject to parliamentary approval.

Choi said the South Korean military should speed up an upgrade of the current missile defense and acquire surveillance satellites to establish independent Korea Air and Missile Defense (KAMD) and a pre-emptive missile destruction system, the so-called "Kill Chain."

"South Korea and U.S. forces should deter North Korea from using its nuclear weapons using a joint deterrence strategy," the 59-year-old Choi said during a parliamentary confirmation hearing.

"If there is a possibility of the North using (nuclear weapons) and imminent danger, we have to launch a pre-emptive strike using the kill chain. If there's still a nuclear threat, we have to counter it using the KAMD."

South Korea currently operates 48 PAC-2 missiles imported from Germany, which have an interception rate of less than 40 percent.

As part of a mid-term defense plan, the military plans to upgrade the current system to the "hit-to-kill" PAC-3 developed by Lockheed Martin with improved guidance accuracy, and adopt military satellites and spy drones.

North Korea is believed to have more than 1,000 missiles of varying types, with most only able to target South Korea and some capable of hitting some Japanese and U.S. military bases.

Pyongyang fired off a long-range rocket last December and conducted its third atomic test in February as part of efforts to produce a nuclear warhead with a greater range. Seoul's spy agency recently confirmed that Pyongyang has restarted a 5-megawatt plutonium reactor in Yongbyon.

"Considering the nuclear development so far, I believe (North Korea) has made considerable progress in warhead miniaturization," Choi said.

Choi also pledged to strike back against any provocations by North Korea, which killed 50 South Koreans in 2010 in a torpedo attack against a Navy warship and the shelling of a western border island. 

"I will strike the origin of attack as well as its command and supporting forces to stop any further provocations," Choi told lawmakers of the parliamentary defense committee.

Choi's appointment comes at a critical time as South Korea is preparing to regain its wartime operational control (OPCON) from the U.S. in December 2015, which will change the military command structure if implemented.

Following Pyongyang's third nuclear test and its bellicose rhetoric, Seoul has asked Washington to postpone the schedule to have more time to bolster its defense capabilities. Consultations are currently underway between the two governments to reach an agreement on the appropriate timing for the transfer.

Although Choi supported South Korea's taking back its wartime command, he said Seoul and Washington should review the changing regional situation to set the right timing for the transition.

"The OPCON transfer has a great impact on the security situations on the Korean Peninsula. We have to consider the conditions for the transition, rather than a just cause," he said.

"The transition should take into consideration the rising threat by North Korea's nuclear and missile weapons and (the South Korean forces') deterrence capabilities."

South Korea handed over its OPCON to the U.S.-led United Nations troops during the 1950-53 Korean War and subsequently regained peacetime OPCON in 1994. 

Currently, the South Korean military remains in command under normal armistice circumstances, but the U.S. commander would assume OPCON of the two nations' forces if war broke out. (Yonhap News)