People Power Party presidential candidate Yoon Suk-yeol on Thursday defended his position on "preemptive strike" against North Korea, saying that such a plan would curb war and protect peace in a live broadcast TV debate on Thursday.

"The president should exercise leadership to prevent the war itself from happening. I think it’s a rash remark," Sim Sang-jeung of the Justice Party told Yoon in the debate.

In response, Yoon said, "We are not trying to wage war, but to curb it," adding, "The kill chain, which is called a preliminary blow, is to protect peace."

However, Sim said, "The effectiveness of the kill chain is limited. A preemptive strike is going straight to war. It is like a declaration of war."

Earlier, Yoon said at the New Year’s press conference said, "When there are signs that (North Korea is launching a missile toward the South), there is no other way to stop it except the preemptive strike of the kill chain, which is at the forefront of the 'three-axis system'."

The three-axis system refers to the South Korean military response system to North Korea. The first axis is a kill chain that preemptively strikes North Korean nuclear and missiles, the second axis is a "Korean missile defense system" that intercepts missiles shot by North Korea and the third axis is a "mass retaliation."

At the debate, there was a battle between Lee Jae-myung, the presidential nominee of the ruling Democratic Party, and Yoon over the additional deployment of Terminal High Altitude Area Defense.

Lee asked Yoon, "Why are you trying to install it again to cause China’s backlash and ruin the economy?" saying THAAD does not help defend the Seoul metropolitan area.

Yoon replied, "North Korea often launches missiles at high angles, so the Seoul metropolitan area also needs (THAAD)."

As for the location of the deployment, Yoon said, "Even if it is not necessarily the metropolitan area, the location is a matter that should be decided by the military."

The issue of nuclear sharing was also put on the table.

People Party leader Ahn Cheol-soo suggested Yoon about signing a nuclear sharing agreement between South Korea and the US to cope with the North Korean nuclear threat. Yoon said, "That is also part of the extended deterrence," adding, "It can be solved by strengthening the Korea-US alliance and strengthening the extended deterrence."

Extended deterrence is a commitment to deter and, if necessary, to respond across the spectrum of potential nuclear and non-nuclear scenarios in defense of allies and partners.