People who live near the deployment site say the presence of the US anti-missile system is a risk to their security. Candidates running for the May 9 presidential election are split over the issue.
Security is a hotly contested issue in South Korea's upcoming presidential election. In particular, candidates are divided over the controversial THAAD anti-missile defence system.
Terminal High Altitude Area Defense, or THAAD, has divided the South Korean public as well. And it has become a major issue in the country's presidential race. The anti-missile system which has reached initial operational capacity will not be fully functional for a few months, the US has said.
South Korea's nineteenth presidential election is set to be held on May 9, to determine a successor to Park Geun-hye, who was dismissed last month over a corruption scandal.
What do the candidates want
Liberal frontrunner Moon Jae-in had originally criticised THAAD but has since eased his position. If elected, Moon, is expected to somewhat soften South Korea's policy towards North Korea.
Moon's closest contender, moderate candidate Ahn Cheol-soo has been criticised for flip-flopping on the THAAD issue.
Ahn has toughened his approach on national security in an attempt to garner more conservative votes, according to analysts.
More conservative candidates are very much pro-THAAD. Bareun Party candidate Yoo Seong-min said he would deploy more THAAD batteries if elected.
But far-liberal candidate Sim Sang-jung is vehemently against the anti-missile system.
"Basic democratic procedures and the process of having national interest discussions were not undertaken when THAAD was decided under the Park Geun-hye administration. That's why THAAD has caused so much social discord," said Sim, presidential candidate of the Justice Party.
But with THAAD initial operational status, experts are sceptical if the next president will have the authority to backtrack on the plan.
China on Wednesday called on all parties in the Korean standoff to stay calm and "stop irritating each other" a day after North Korea said the United States was pushing the region to the brink of nuclear war.
The United States has urged China, reclusive North Korea's lone major ally, to do more to rein in its neighbour's nuclear and missile programmes which have prompted an assertive response from the Trump administration, warning that the "era of strategic patience" is over.
The United States has sent a nuclear-powered aircraft carrier to Korean waters and a pair of strategic US bombers flew training drills with the South Korean and Japanese air forces in another show of strength this week.
Chinese Foreign Ministry spokesman Geng Shuang, asked about the bomber flights, the drills and North Korea's response, stressed that the situation was "highly complex" and sensitive.
"The urgent task is to lower temperatures and resume talks," he told reporters.
Trump has stepped up outreach to allies in Asia to secure their cooperation to pressure North Korea, and over the weekend he spoke with the leaders of Thailand, Singapore and the Philippines in separate phone calls.
The US ambassador to Indonesia, Joseph R. Donovan, told reporters Indonesia was among several countries that the United States was urging take a "fresh look" at their North Korea ties.
Trump's calls to the Asian leaders came after North Korea test-launched a missile that appeared to have failed within minutes, its fourth successive failed launch since March. It has conducted two nuclear tests and a series of missile-related activities at an unprecedented pace since the beginning of last year.
Chinese President Xi and his Philippine counterpart, Rodrigo Duterte, discussed the Korean situation by telephone on Wednesday, China's Xinhua state news agency said.
North and South Korea are technically still at war after their 1950-53 conflict ended in a truce, not a peace treaty. The DPRK regularly threatens to destroy the United States, Japan and South Korea.