US to ramp up its military presence in South Korea
Seoul and Washington have discussed the deployment of US strategic military assets to the Korean peninsula, according to a South Korean military official, after North Korea detonated what it claims was a hydrogen bomb.
The two governments have declined to provide details of what those assets might be, but analysts suggest they could include the deployment of the THAAD anti-ballistic missile system in South Korea and an increased presence by the US 7th Fleet in waters off the east coast of the peninsula.
In early 2013, another period of escalated tensions in the region, the US sent a nuclear submarine to the region and carried out sorties of nuclear-capable B-2 and B-52 bombers in South Korean airspace. A similar show of force is very possible, the experts suggest.
Pyongyang's latest act of belligerence may even prompt new discussions on the reintroduction of US tactical nuclear weapons into the South. The last such weapons were withdrawn in the early 1990s, although South Korea remains firmly under Washington's nuclear umbrella.
Both governments remain reluctant to push ahead with the reintroduction of US nuclear weapons to the peninsula, but there are some in the South who insist they should remain an option.
"The US and South Korea are being intentionally vague on their possible reactions, but it is likely that they are considering exo-atmospheric interceptors," Lance Gatling, a defence analyst and president of Nexial Research Inc, said. "They are involved in a strategic and diplomatic tit-for-tat at the moment, with the North's nuclear test raising the technical and threat levels, meaning the South and the US have to respond by raising their defence levels."
North Korea took the world by surprise when it announced on Wednesday that it had successfully tested a hydrogen bomb. Although most analysts doubt the claim, and seismic data suggests it was more likely to have been a less powerful atomic bomb of the sort it has detonated three times before, the test provoked a wave of international condemnation.
Han Min-koo, the South Korean defence minister, said the military was exploring possible responses to the latest North Korean provocation, including resuming propaganda broadcasts through loudspeakers across the Demilitarised Zone that divides the two nations.
Similar broadcasts triggered a brief exchange of artillery fire in August of last year.
Washington has reiterated its "ironclad defence commitment" to South Korea during a telephone discussion between Mr Han and Ashton Carter, the US defence secretary, with Yonhap News reporting that the agreement "includes all kinds of extended deterrence assets".
John Kerry, the US secretary of state, confirmed Washington's position that the test was a "highly provocative act" and an unacceptable challenge to the international community, as well as a clear violation of UN Security Council resolutions on North Korea for its nuclear and missile programmes.
President Barack Obama also held talks with Shinzo Abe, the Japanese prime minister, in which he reaffirmed the US commitment to Japan's security. The two leaders agreed to "work together to forge a united and strong international response to North Korea's reckless behaviour", the White House said.