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 on Monday.

“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 United States about the deployment of Thaad, which is short for Terminal High Altitude Area Defence. North Korea’s recent actions have changed that, with defence officials saying in Seoul they cannot 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.”

South Korea opening to Thaad may increase calls in Japan to follow suit. Defence Minister Gen Nakatani said in November that Japan was considering the deployment of Thaad to counter any potential strike from North Korea, although Chief Cabinet Secretary Yoshihide Suga said on Monday that the country had no plan at the moment to introduce the system. 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.

“From North Korea’s perspective, Thaad is a big problem, because it reduces the probability of a successful attack,” said Jack Midgley, defence industry consultant with Deloitte Tohmatsu Consulting in Tokyo. “For a DPRK planner, this means that to have an assured successful attack, he needs to fire a lot of missiles — not just one or two. And the DPRK doesn’t have that capability. So Thaad reduces the value of nuclear threats by DPRK.”

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. China supplies most of North Korea’s energy and food imports and the US called on Beijing to curb that trade.

Secretary of State John Kerry failed last month during a visit to Beijing to secure China’s support for tougher sanctions, with the countries agreeing only to pursue a new United Nations Security Council resolution. The US has sought measures such as bans on oil exports to Pyongyang.

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 based on national security interests. And the latest South Korean announcement deepens her change of stance. Just in September she went to Beijing to congratulate President Xi Jinping on China’s World War II victory, while US President Barack Obama and Japanese Prime Minister Shinzo Abe stayed away.

“Park expended a lot of political capital in going to Beijing for the 70th anniversary military parade and has received nothing, or a slap in the face, in return,” said Ralph Cossa, president of the Pacific Forum CSIS in Honolulu. “It was naive to ever expect China to ‘tilt’ towards the South, but there were hopes it would respond objectively to future North Korean provocations.”

The US has played down China’s concerns about Thaad, saying the system is defensive and focused on North Korea. Still, its closer deployment to the Chinese border has the potential to exacerbate strains stemming from territorial disputes involving China in the East China Sea and South China Sea.

“It might very likely propel China to go along with its offensive missile system and put in more effort into its rather nascent missile defence programme,” said Collin Koh Swee Lean, an associate research fellow at RSIS. “In the case of North Korea, in the case of China, they’ll be keen to come out with new ballistic missiles that have the ability to decoy incoming projectiles trying to intercept it and to mislead missile defences so as to have a higher chance of hitting the target.”

By arrangement with Bloomberg-The Washington Post

Published in Dawn, February 9th, 2016