"Demand for democracy is particularly high because of the candlelight revolution, and demand for democratic procedural legitimacy for the THAAD deployment is, therefore, high," Moon told the U.S. Congress earlier this month during a visit to Washington.
The former human rights lawyer, who also repeatedly questioned THAAD during his election campaign, reassured Congress that his demand for a probe wasn't a reversal of deployment plans.
In May, the president discovered that four additional THAAD missile launchers were installed without his knowledge — a realization that triggered an official probe into the entire system.
"These procedural issues, along with the fact that a full environmental review of the deployment area was not previously conducted, raised concerns among the Korean public," Gibson said.
The situation is a red flag for Washington, which has long pressed for swift missile defense implementation.
"I'm troubled by the fact that it is now going to be resubmitted for political debate in the Republic of Korea as to whether or not they will accept our $923 million investment in missile defense for their country," U.S. Sen. Dick Durbin said in a June 7 hearing. "I can't follow their logic here."