South Korea's presidential office expressed displeasure Wednesday at China's ferocious opposition to its push for the deployment of THAAD, a U.S. missile defense system, here.

It is a matter of "self-defense" against North Korea's nuclear and missile threats, Cheong Wa Dae spokesman Jeong Yeon-guk told reporters.

He was responding to increased public pressure from China over the THAAD issue.

Beijing's top envoy in Seoul warned Tuesday that bilateral ties will be destroyed "in an instant" if the Terminal High Altitude Area Defense system is positioned on the peninsula.

In a meeting with Kim Jong-in, head of the main opposition Minjoo Party of Korea, Ambassador Qiu Guohong was also quoted as saying South Korea's own national security may be jeopardized as well.

He even argued the THAAD issue has slowed consultations in the U.N. Security Council on additional sanctions.

Qiu's remarks, quite unusual for a senior diplomat, were seen by many as Beijing putting explicit pressure on Seoul.

China views a THAAD unit in Korea as targeting not only North Korea but also China. It is especially concerned about its high-powered radar.

The Cheong Wa Dae official stressed that it is a self-defense measure for South Korea to allow the U.S. Forces Korea to deploy THAAD in the country. He cited the North's growing military threats.

"It's a matter to be decided in accordance with security and national interests, and China will have to recognize the point," Jeong said.

In a separate statement, South Korea's Foreign Ministry emphasized that North Korea is the fundamental reason for considering THAAD on its soil.

"If (China) raises the THAAD deployment issue, it would be reasonable to take a look first at why the matter has occurred," it said.

It said the THAAD discussion and efforts to adopt a U.N. resolution are separate affairs.

"It's important for the two countries to make joint efforts on the basis of mutual trust," said the ministry.

It added that it is taking "necessary" steps with regard to Qiu's comments.

An informed source told Yonhap News Agency that the ministry initially considered calling him in to confirm Beijing's view on the matter and explain Seoul's position.

But some officials raised the need to give an impression that South Korea is not overreacting, given the significance of Seoul-Beijing relations, another source said.

In Washington, U.S. Secretary of State John Kerry and his Chinese counterpart Wang Yi held talks on North Korea and the THAAD issue.

They produced "significant" progress on the U.N. resolution but failed to narrow differences on the THAAD dispute.

Kerry said there would be no need to deploy THAAD on the peninsula should North Korea move to abandon its nuclear weapons program and stop its military threats. (Yonhap)