South Korea can expect Chinese opposition if it allows American defence system to be deployed on its soil.

The United States has opened the door to parking a ballistic missile defence system on North Korea's doorstep, a move that could reshape North Asia's security landscape.

Kim Jong Un's weekend launch of a long-range rocket prompted a reaction that his nuclear test last month did not: South Korea now says it will consider allowing the deployment on its soil of a US army system known as Thaad.

For years South Korea has danced around the idea of Thaad, which targets missiles at high altitudes and could complement lower-altitude defences already in the country. That's mainly because it risks annoying neighbour China, which has warned against Thaad being deployed on the Korean peninsula. It could also spur Japan to look at using it.

President Barack Obama is trying to work all sides. He spoke with Chinese President Xi Jinping a few days before the launch "about the need to really tighten the noose" on North Korea, agreeing to a verifiable denuclearisation of the Korean Peninsula, Obama said in an interview with CBS aired yesterday.


"But what we're also doing is consulting with the South Koreans for the first time about more missile defence capabilities to prevent any possibility that North Korea could reach US facilities or US populations," Obama said.

While Thaad could be a deterrent against Kim's regime, it would also raise the stakes for security in a region where suspicions already run high over Japan's military aggression during World War II and a later conflict that split the Korean peninsula between an isolated, unpredictable regime in the north and what is now a democracy in the south.

"The Chinese are doing anything possible to head off what they think might be a potential weapon that could be used against them," said Richard Bitzinger, a senior fellow at the S Rajaratnam School of International Studies in Singapore. "You can say everything you want, that this is not directed against the Chinese, but the fact of the matter is, it potentially could be."

South Korea has long assured China, its biggest trading partner, it was not in talks with the US about the deployment of Thaad, short for Terminal High Altitude Area Defence. North Korea's recent actions have changed that, with defence officials saying in Seoul they can not afford to ignore calls for a stronger shield against weapons of mass destruction.

"It would draw ridicule for a sovereign nation like South Korea not to beef up its defence in the face of an increasing threat like North Korean nuclear missiles," said Park Chang Kwon, a senior research fellow at the state-run Korea Institute for Defence Analyses in Seoul. "Thaad helps deter North Korea from seeking nuclear arms because it sends a strong message South Korea is and will keep responding with tough actions."

Japan may follow suit.

Japan and South Korea already both have Patriot missiles and the countries, alongside China and India, are among the biggest spenders on defence in Asia.

The system would only be deployed on US bases in South Korea - there are nearly 29,000 US soldiers stationed there - and talks on the terms for that have no clear timetable. The discussions could face resistance from a South Korean public wary of hurting ties with China. But it would also send a message to Beijing that it should do more to rein in North Korea by using its influence.

While South Korea has sought to deepen ties with China since President Park Geun Hye took office in 2013, it has been frustrated by China's failure to stop Kim testing nuclear devices. China warned last year that the use of Thaad would risk undermining ties, saying the Park government should reject the system in the interest of peace and stability of the whole region.

Days after what North Korea claimed was the detonation of its first hydrogen bomb, Park said publicly she would consider Thaad deployment. And the latest South Korean announcement deepens her change of stance.

- Washington Post, Bloomberg