SOSEONG-RI, SOUTH KOREA (REUTERS) - Outside a small farming village four hours south of Seoul, elderly farmers wearing T-shirts reading "Let's harvest peace by ousting Thaad" work in melon fields before marching in protest against the controversial US anti-missile system.

While many South Koreans have welcomed the reduced tensions with North Korea as Washington and Pyongyang talk about ending decades of hostilities, the village of Soseong-ri is anything but peaceful.

Soseong-ri is home to the Terminal High Altitude Area Defense (Thaad), a state-of-the-art system designed to protect against North Korean missiles.

But Thaad has also angered Pyongyang and its main backer, China, and made Soseong-ri nervous it would be a potential target if hostilities between the old enemies resume.

Residents also complain of the noise from the generators that power Thaad humming around the clock and helicopters shuttling fuel and supplies, and worry about electromagnetic waves from the system's radar possibly damaging their crops.

For the past 680 days, around 200 villagers have been taking shifts around the clock to try to block US vehicles travelling to the battery site.

Since US President Donald Trump and North Korean leader Kim Jong Un's historic meeting in Singapore last month, residents of Soseong-ri say there is less need for the system.

"Take Thaad out, the North Korean nuclear threat is gone,"one banner reads as a group of 40 men and women in their 60s, 70s and 80s walk past a wall painted "No Nukes, No Thaad."

Lee Jong-hee, a 61-year-old farmer, leads a twice-weekly rally outside the US army base, built on a former golf course.

"Now the North Korean nuclear and missile threat has (abated) conspicuously. As it is declared that there will be no more war on the Korean peninsula, there is no reason for Thaad to be in my country," said Lee, who hopes the system could be withdrawn within three months.

"How do North Korea and the United States begin peace talks without this war weapon being removed?," Lee told Reuters at his farm while his aged mother packed boxes of yellow melons.

HOW LONG DOES IT STAY?

Trump and Kim Jong Un last month agreed to work toward complete denuclearisation of the Korean peninsula, although they made no mention of how or when Pyongyang might give up its nuclear weapons programme.

Trump has cancelled joint military exercises with South Korea scheduled for August, calling the war games "provocative"and "expensive".

But experts say it will be a long while before the United States considers withdrawing Thaad, which was deployed last year.

After initial troubles getting components in, the system is now complete with six launchers and a powerful X-band radar that constitute one Thaad battery.

The US military would want to keep Thaad at least through the end of the denuclearisation process, expected to take several years, analysts and former officials say.

"Thaad is part of a layered defense of the US ground forces in (South Korea) against the threat from North Korean ballistic missiles," said Daniel Russel, former assistant secretary for East Asia and now at the Asia Society Policy Institute.

"There is no military rationale for withdrawing the Thaad system as long as Pyongyang maintains an arsenal of ballistic missiles and as long as US Forces remain in Korea."

Maintaining Thaad would also keep pressure on China to maintain sanctions on North Korea until it fully decommissions its nuclear weapons.

"It was China, not North Korea, that was the most uncomfortable with the idea of deploying Thaad in South Korea," said Yang Uk, a military expert at the Korea Defense and Security Forum.

Beijing opposed Thaad and its powerful radar that can see deeply into Chinese territory, saying it upsets the regional security balance.

In retaliation to the Thaad deployment, Beijing imposed unofficial boycotts on South Korean businesses and banned group tours to South Korea.

"Thaad can work as a leverage against China, because the more China cooperates with North Korea's denuclearisation, the more likely they can say goodbye to Thaad," said Yang.

Chinese defence ministry spokesman Wu Qian, asked last week whether China had again requested Thaad be withdrawn in the light of the Trump-Kim summit, said it is "resolutely opposed to the United States deploying Thaad in South Korea."

Spokespeople for South Korea's presidential Blue House and the US Forces in Korea said there has been no discussions about the system's future following the Singapore summit.

Seoul's defence ministry is preparing an environmental study to assess how the missile defense system will impact the 70 hectare (172 acre) site granted to the US army to host the battery.

Back in Soseong-ri, protesters are preparing themselves for a long fight.

"We can endure the physical exhaustion of coming to protests every day or occasionally clashing with police," said Kim Jong-hee, a 50-year-old mother who joined Wednesday's protest from the nearby town in Gimcheon.

"The harder thing is how we have to live with the fact that we can't really stop this no matter how we resist physically," Kim said. "It's so agonizing because this is now the way people here have to live."