Residents of Dongducheon are opposed to the decision to keep some U.S. troops at Camp Casey, which is based in the northern city.
The decision was part of an agreement with the United States to delay the transfer of wartime operational control (OPCON) of South Korean troops to Seoul.
Speaking to reporters Friday, Dongducheon Mayor Oh Se-chang voiced his opposition. "The unilateral announcement to leave the unit in the city is killing local residents," he told them. "We will fight to block the decision by every means possible."
Defense Minister Han Min-koo and U.S. Secretary of Defense Chuck Hagel agreed to keep the 210th Armored Brigade in Dongducheon instead of moving the entire 2nd U.S. Infantry Division (2nd ID) to Pyeongtaek during their meeting in Washington, Thursday.
The joint communique issued after the annual Security Consultative Meeting (SCM) stipulates that the unit will stay put for at least six years "until the ROK forces' counter-fire reinforcement plan is completed and certified."
The two allies had originally planned to move the entire 2nd ID to Pyeongtaek by 2016.
"The citizens' anger is reaching a limit," said Rep. Jung Sung-ho of the main opposition New Politics Alliance for Democracy (NPAD), whose constituency includes the city. "Camp Casey is in the middle of Dongducheon. The city had been planning to redevelop the area for future generations after the camp moved to Pyeongtaek. The agreement at the SCM is contrary to citizens' expectations."
Col. Wee Yong-sub, the defense ministry's deputy spokesman, told a regular briefing: "We will closely work with the relevant parties to address the anger of the residents."
Regarding OPCON, the defense ministry said South Korea is seeking to regain this from Washington by 2023.
Controversy has surrounded the decision made at the SCM to delay Seoul's takeover of wartime OPCON until its military capability is secured. Critics have argued that the decision appears to be an indefinite delay of the transition.
"Saying an indefinite delay is a jump of logic," Minister Han told reporters after the annual talks. "Seoul has plans to improve its defense capabilities against the nuclear and missile threats from North Korea. Transition will be possible after 2020."
Yoo Jeh-seung, deputy defense minister for policy, said regaining wartime operational control depends on when Seoul completes its own Kill Chain preemptive strike and Korean Air and Missile Defense systems.
"We expect the projects to be completed in 2023," he said.
With regard to the controversy surrounding President Park Geun-hye for breaking her campaign pledge to retrieve wartime OPCON by the end of 2015, Cheong Wa Dae spokesman Min Kyung-wook said, "A cool-headed assessment of the situation is necessary at this stage amid mounting threats from Pyongyang."
"A stable transition will contribute to the ultimate deterrence of the North's provocations and enhancement of the Seoul-Washington joint defense capabilities," he added.
Follow Jun Ji-hye on Twitter @TheKopJihye