The deployment of THAAD was agreed upon between the US and South Korea previous year, but has been delayed due to environmental impact assessments and diplomatic issues.
"If all this begins to unfold at such alarming rates, then inevitably, then at some moment, the question will probably arise as to our response in military terms of creating some counterbalances", the senior diplomat noted.
South Korea's defense ministry said Wednesday that the US military will install the four additional THAAD launcher early Thursday morning. "THAAD is a missile defense system for the theater of operations".
Russian Federation and China are concerned over the deployment of these systems in the area.
In Beijing, Chinese Foreign Ministry spokesman Geng Shuang expressed grave concerns over the planned additional installation as he urged South Korea and the United States to withdraw the THAAD system.
The leaders of Russian Federation and South Korea have condemned North Korea over its latest nuclear test, but still appear far apart on the issue of stepping up sanctions against Pyongyang.
A number of countries have firmly condemned North Korea's test calling for retaliation.
The ministry stressed the urgent need to mobilize the launchers amid growing threats from North Korea, which had its sixth and most powerful nuclear test on Sunday. There are now two launchers at the location.
"Myself and President Putin share a view that North Korea has gone the wrong way with its nuclear and missile programme and that easing tension on the Korean peninsula is an urgent issue", Mr Moon said.
The missile defense system will be deployed already tomorrow on a new basis in Seongju 300 kilometers from Seoul together with the construction technique and all related materials.
President Donald Trump has spoken with German Chancellor Angela Merkel to discuss the latest provocation by North Korea.