South Korea said Wednesday it would make an “independent decision” over the U.S. potential deployment of an advanced missile defense asset to Korea, based on its calculation of security interests and the system’s military efficacy.

The statement was seen to reflect a subtle change in Seoul’s position over the much publicized emphasis of senior U.S. officials on the need for deploying the Terminal High Altitude Area Defense system here. It also showed Seoul’s dilemma over the contentious deployment that is hotly debated domestically, although the allies have yet to begin any official consultations over it.

“(South Korea) will make its own, independent judgment and decision based on its comprehensive consideration of (THAAD’s) military efficacy and national security interests,” Cheong Wa Dae spokesperson Min Kyung-wook told reporters.

“We understand that an internal consultation process is still ongoing in the U.S., and the results are yet to come out.”

Earlier this week, U.S. Secretary of State John Kerry and U.S. Forces Korea Commander Gen. Curtis mentioned the need for THAAD, reigniting the controversy over its deployment, which China and Russia believe could target them and undermine their security interests.

The controversy further escalated as another senior U.S. official said Tuesday that Washington is considering “permanently stationing” a THAAD battery in Korea, although no internal decision has been made yet.

“Although we’re considering the permanent stationing of a THAAD unit on the Korean Peninsula, we have not made a final decision and we’ve had no formal consultations with the Republic of Korea on a potential THAAD deployment,” Frank Rose, assistant secretary of state for arms control, verification and compliance, said at a security seminar in Washington D.C.

“However, let me be clear on a couple of points. THAAD is a purely defensive system that would improve our ability to intercept short- and medium-range missiles from North Korea. It does not and cannot impact broader strategic stability with Russia or China.”

Touching on China’s dogged opposition to the THAAD deployment to Korea, Rose said China appears to be using the THAAD issue to disrupt Washington’s regional alliance system.

“I think part of what China is trying to do is create a wedge in the U.S. alliance system in the region,” he said.

U.S. officials’ mention of THAAD came amid growing public angst here over North Korea’s evolving nuclear threats including those from its submarine-launched ballistic missiles. Pyongyang recently claimed it succeeded in conducting an underwater test of the SLBM.

As Rose noted, some experts have raised the possibility that the THAAD issue could undercut the South Korea-U.S. alliance with Seoul showing reluctance over the dispatch and seeking to strengthen its partnership with China, its largest trading partner.

Some observers say that the THAAD issue is expected to be included in the agenda for the summit between South Korean President Park Geun-hye and U.S. President Barack Obama in the U.S. next month. Cheong Wa Dae refused to comment on the agenda.

Seoul has so far maintained the so-called “3-noes,” arguing that there have been no consultations between the allies, no request from the U.S. for any official talks and no decision reached.

But with Washington officials apparently raising pressure on Seoul to positively consider the deployment, the 3-noes policy can no longer be maintained, observers said.

The THAAD is a core element of the U.S.’ multilayered missile defense program. It is designed to intercept short-, medium- and intermediate-range ballistic missiles at altitudes of 40 to 150 km during the terminal phase of flight after detecting the missiles with land-based radar that has a maximum range of about 1,800 km.

A THAAD battery consists of six truck-mounted launchers, 48 interceptors (eight per launcher), a fire control and communications unit and an AN/TPY-2 radar.

By Song Sang-ho (sshluck@heraldcorp.com)