The US military in South Korea said Friday that the deployment process of the US advanced missile defense system in South Korea was “transparent,” in response to President Moon Jae-in’s claim that the process was mysteriously accelerated.

In an email to The Korea Herald, the United States Forces Korea said that the US was fully transparent with the Korean government throughout the process, highlighting that Washington trusts South Korea’s official stance that the THAAD deployment was an alliance decision.

“The US trusts the (South Korean) official stance that the THAAD deployment was an Alliance decision. We have worked closely and have been fully transparent with the (South Korean) government throughout this process,” the USFK Public Affairs Office said.

The USFK, however, declined to comment on when the deployment would be finished and whether the process should undergo environmental assessment, citing operational security. Moon said that the deployment is subject to an environmental assessment that could take at least six months.

The announcement came amid controversy over Moon, who said in an interview with Reuters Thursday that “for the reasons unknown to him,” the allies have deployed the entire set of a THAAD battery, although they had initially agreed to deploy only one launcher this year.

Two THAAD launchers are stationed in Seongju, North Gyeongsang Province, with the other four launchers stored in a US base in the southern part of the peninsula. The existence of the four launchers was not revealed to the public until last month.

The controversy is likely to weigh on Moon’s fist summit with US President Donald Trump, who was allegedly “indignant” over the South Korean government’s dealing with the THAAD deployment. Trump also demanded South Korea pay for THAAD, whose cost he estimated $1 billion.

In an attempt to minimize diplomatic impact, presidential office Cheong Wa Dae stressed that the president’s remark was designed to ensure “procedural legitimacy,” not an attempt turn the THAAD negotiation in its favor ahead of the summit scheduled on June 29-30.

“The president’s remark came as a part of his effort to explain that the South Korean government is not trying to postpone (the deployment of THAAD). It was aimed to highlight the government’s effort to follow the legitimate process for the deployment,” Cheong Wa Dae spokesperson Park Soo-hyun said.

Seoul’s Defense Ministry declined to comment on exactly what sort of agreement the allies made over THAAD when they decided to deploy the platform last year.

“There is nothing we can tell you beyond what the president said during the Reuters interview,” said a ministry official under the condition of anonymity.

Since Cheong Wa Dae found out last month that there was four THAAD launchers deployed on the peninsula without their knowledge, the government temporarily halted the stationing process by ordering an environment assessment on the THAAD battery site.

The measure came after the allegation that Seoul’s Defense Ministry deliberately dropped information about the four launchers from their report to presidential security advisers. The investigation is still underway over how and why such a decision was made.

By Yeo Jun-suk (jasonyeo@heraldcorp.com)