But after North Korea fired intercontinental ballistic missiles in July, Moon ordered aides to start discussions with the USA on deploying four additional mobile Thaad launchers.
The THAAD systems will be deployed on Thursday at a new base in Seongju, 300 kilometers (186 miles) from Seoul.
The decision was made by the Moon Jae-in Government in the face of growing tension sparked by North Korea, which conducted its sixth and most powerful nuclear test on Sunday.
Four more THAAD anti-ballistic missile launchers will be installed this week at a United States military base in South Korea, Yonhap news agency reported on Wednesday, citing South Korea's defence ministry. The protesters said the deployment will begin at 2 a.m. Thursday, but the Defense Ministry refused to confirm the time.
A THAAD battery normally consists of six launchers, but only two have been operational so far at the site in rural Seongju.
Although focused on deterring North Korea, China and Russian Federation see the system as harmful to their security interests.
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The deployment comes amid heightened tensions on the Korean Peninsula over North Korea's missile and nuclear tests.
The four remaining launchers have been on standby at an unidentified USA base in South Korea, pending the alliance's decision.
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.
Speaking after the talks with the visiting South Korean president, Putin in televised remarks urged North Korea's neighbors to support the Russian-Chinese roadmap.
"To be more precise, I think it is altogether impossible", he added.
Tensions between the U.S. and North Korea threaten to have devastating consequences for South Korea.