Pentagon spokesperson Captain Jeff Davis told journalists on May 30 that the U.S. Department of Defense has been very transparent in all its actions throughout the deployment of the THAAD missile defense system in South Korea. Davis was responding to the report that four additional launchers were secretly added to the THAAD system, and that President Moon Jae-in has ordered an inquiry into the actions, Yonhap News Agency reported on May 31.

Davis pointed out that THAAD has developed the initial operating capability to defend against missiles, and promised that the U.S. will continue to work very closely with the South Korean government to upgrade the system and equip it further.

Moon was shocked to learn of an additional four launchers brought into the country, in addition to the two that were already installed. He quickly ordered a probe into the matter.

Moon's special envoy, Lee Hae-chan, said on May 19 during a visit to China that South Korea understands China's concerns and is ready to strengthen coordination with China to remove any obstacles to the development of bilateral ties.

China opposes the deployment of the Terminal High Altitude Area Defense (THAAD), an advanced U.S. missile defense system, in South Korea.

Chinese Foreign Minister Wang Yi noted on May 22 that "whoever tied the bell to the tiger shall take it off," implying that China wants South Korea to take concrete steps to eliminate the friction in their bilateral relations, and that China is willing to maintain communication with South Korea over the issue.