During talks with his South Korean counterparts in Seoul on Monday, Liu Jianchao, the Chinese assistant foreign minister, pointedly made Beijing's position on the Terminal High-Altitude Area Defense (THAAD) system clear.

Speaking to local media after the meeting, Liu said he had informed his hosts that "Beijing would be grateful should [Seoul] think of China's concerns."

"We hope that the US and South Korea will make an appropriate decision over the potential deployment of THAAD," he added.

China insists that its concern is that THAAD poses a threat to other nations in the region even though Washington wants to provide it to its South Korean ally as an additional layer of protection from the threat posed by North Korea's ballistic missiles.

Analysts say that China's fears are a smokescreen for its true intentions as THAAD is a purely defensive system that is designed to intercept and destroy short, medium and intermediate missiles - pointing out that it carries no warhead and "kills" an incoming projectile simply by colliding with it.

Seoul is aware of the importance of its military alliance with the US

'A political issue'

"The Chinese People's Army has been quiet about the system, so it's clear to me that this is a political issue," Daniel Pinkston, a Korea analyst with The International Crisis Group in Seoul, told DW.

"This pressure is designed to undermine the security alliance between South Korea and the US and China is playing the long game as it tries to win over Seoul," he said.

Beijing has been courting the South Korean leadership in recent years, through trade agreements, as well as political and cultural exchanges designed to bring the two nations' peoples closer together. Most recently, China has been pushing for South Korea to be a founder member of the Asian Infrastructure Investment Bank, one of Beijing's initiatives for the region but seen elsewhere as an effort to rewrite the regional financial order in Beijing's favor.

China's pressure has placed Seoul in a difficult political position. It recognizes the benefits that would result from closer economic ties with China - as well as the gentle pressure Beijing could exert should it not get its way, such as by refusing to issue visas swiftly or by delaying or cancelling investments - but Seoul is similarly aware of the importance of its long-standing security alliance with the US.

Washington has been the guarantor of South Korea's existence since the Korean War broke out in 1950 with an unprovoked invasion from the Communist North. More than 28,000 US troops are based in the country as a deterrent against the regime in Pyongyang, which continues to invest heavily in nuclear weapons and missile delivery systems.

Seoul on the fence

Seoul, for now, is sitting on the fence. The government has conceded that THAAD would be a helpful asset for the defense of the South, but in statements it has claimed it has received "no requests" from Washington to deploy the missiles, that there have been "no consultations" and that "no decision" has been reached.

And while both governments are sticking to that line, it emerged last week that US Forces Korea have carried out a series of surveys to determine the most appropriate sites to deploy the mobile THAAD launchers.

On Tuesday - one day after Liu arrived in Seoul - Daniel Russel, the US assistant secretary of state for East Asian and Pacific affairs also landed in the South Korean capital for talks. Speaking to reporters ahead of the meeting, Russel said, "The foundation of the alliance is rock-solid."

A former head of the South Korean National Intelligence Service told DW that the missile system would "obviously provide greater security" and that the South Korean public was generally happy to leave the issue in the hands of the government to make the best decision.

"It is also obvious that the US is the main provider of our protection and we could not afford to upset Washington because of that," he said.

Both US and China

"On the other hand, the government needs to take into consideration the attitude of China," he added. "My sense is that, if the situation is handled well, we could have both the deployment of THAAD to improve our security at the same time as having closer economic ties with China."

China's pressure has placed Seoul in a difficult political position

He says, however, that there is a growing sense that China is attempting to pull South Korea away from Washington's embrace and to tie it more closely to Beijing's agenda.

Pinkston agrees that is China's ambition. And he warns that South Korea needs to be aware of the possible consequences of shifting its affections to Beijing.

"South Korea wants agreement with China on things like fishing agreements, environmental issues, trade and investment and consular arrangements, but it also wants to be sure that if things do go very bad in North Korea that China will be ready and willing to help," he said. "Is the Chinese government really going to do what a South Korean leader, of whatever political background, wants it to do? No, the Chinese will do what is in China's best interests.

"From China's point of view, it wants to loosen the alliance between South Korea and the US, to peel off Korea and to make it less reliant on Washington for its national security," he added. "But when push comes to shove and if South Korean national security was on the line, Seoul would not abandon its alliance with the US.

"I feel that both sides are setting themselves up to be disappointed," he added.