Additional launchers for a controversial American antimissile system will be installed Thursday in Seongju County, North Gyeongsang, the Ministry of National Defense said Wednesday.
President Moon Jae-in ordered the deployment of additional THAAD launchers soon after Pyongyang launched a second intercontinental ballistic missile in late July.
Amid heightened tension around the North Korean nuke tests, South Korea said it will station an additional four THAAD air defense systems in the country's U.S. military base, local media said.
Mr Moon said the leaders agreed that reducing regional tension and "quickly solving" the security challenges posed by North Korea's nuclear and missile programme were critical.
Although the ministry did not provide an exact time for the installation, a residents' group cited by Yonhap said it had confirmed the plan "through various channels", adding that it was due to take place at 2am local time on Thursday.
Russian President Vladimir Putin has called for talks with North Korea, saying sanctions are not a solution.
The United States assured South Korea and Japan on Wednesday of full extended deterrence, based on both its conventional and nuclear arsenal, against North Korea.
Trump also discussed North Korea's purported hydrogen bomb test with Australian Prime Minister Malcolm Turnbull.
The United States on Monday launched a bid at the UN Security Council to quickly slap the "strongest possible measures" on North Korea in response to its sixth and most powerful nuclear test, but China and Russian Federation argued that diplomatic talks were needed to address the crisis.
We will remind, the first THAAD was deployed in South Korea in may this year. He said it "offers a genuine way to defuse the tensions and a step-by-step settlement".
However, the plan - which China has also urged all parties to "seriously consider" - was previously rejected by Washington, with State Department spokesperson Heather Nauert stating last month that the USA is "allowed" to conduct exercises with its ally and "that's just not going to change".