"We will maintain our principle that the decision for the THAAD installation is a sovereign and self-defense act aimed at protecting the country and its people from North Korea's nuclear and missile threats," Foreign Ministry spokesman Cho June-hyuck said in a regular press briefing.

Earlier in the day, the defense ministry signed a contract with Lotte Group to secure land to host a THAAD battery. Seoul and Washington seek to complete the deployment within this year but it could be done as early as May or July.

China has ramped up its criticism ahead of the land-swap deal.

Beijing has objected to the missile shield's presence in South Korea, saying that it could hurt its strategic security interests.

On Monday, China warned that all consequences and responsibility stemming from deploying THAAD should fall squarely on South Korea and the US, raising concerns that it could intensify retaliation going forward.

Though it is denying any official involvement, Beijing has taken what many see as retaliatory measures, such as toughening rules and regulations zeroing in on Korean firms and products.

"Our government will take every possible step to make sure our companies doing business overseas receive fair treatment," Cho said. "While keeping a close eye on action being taken by China, we are thoroughly exploring relevant countermeasures." (Yonhap)