South Korea supports the US decision to suspend their major combined air combat training, seeking alternative ways to bolster the combined defense posture, Seoul's defense chief said Monday.

In a Singapore meeting with Defense Minister Jeong Kyeong-doo earlier this year, US Defense Secretary Jim Mattis proposed indefinitely postponing the massive Vigilant ACE drill that was slated for December.

It was aimed at helping move forward denuclearization talks with North Korea and reducing the defense budget.

"(I) sympathize actively" with the US offer, Jeong told lawmakers during a parliamentary audit session in Seoul.

The minister, however, pointed out public concerns about a potential impact on national security.

"Even if (the training) is postponed, I will put forward opinions on complementary measures in the Security Consultative Meeting to be held in the US," he added without elaborating.

The minister is scheduled to meet Mattis in Washington, DC this week for the annual SCM.

The annual Vigilant ACE involves hundreds of aircraft, including advanced fighter jets.

Asked about the future of the military's ambitious project to beef up its combat capabilities, he said it will go on as planned despite the current dialogue mood.

It has pushed for the so-called three-axis program -- the Kill Chain pre-emptive strike system, the Korean Air and Missile Defense and the Korea Massive Punishment and Retaliation power.

"For now, there's no change or adjustment plan for the three-axis system," he said.  

Touching on the controversy over the North's position on the Northern Limit Line, the de-facto sea border with the South, Jeong said that working-level North Korean officials have yet to accept the NLL as the maritime border, despite leader Kim Jong-un's apparent recognition of it.

In April, the leaders of the two sides agreed to turn the tense area into a "maritime peace zone." They used the term "NLL" in their joint statement.

President Moon Jae-in said it indicates that North Korean leader Kim Jong-un has virtually recognized the NLL.

The North's navy, however, had continued to claim its own security line until recently, sending repeated warning messages to South Korean ships crossing it. 

That appears to be because North Korea's front-line troops have not received any new related instructions from Kim, Jeong said.

He added that the North's working-level officials have not yet agreed to accept the NLL.

Gen. Park Han-ki, chairman of the Joint Chiefs of Staff, said the South urged the North not to take issue with the NLL during the bilateral general-grade talks last week.

"(We) clearly told (the North) to stop sending such inappropriate radio messages," he said. (Yonhap)