South Korea Seeks US Strategic Weapons after North's Nuclear Test

The United States and weapons experts voiced doubts the device was as advanced as North Korea claimed, but calls mounted for more sanctions against Pyongyang for its rogue nuclear program.

A South Korean military official told Reuters the two countries had discussed the deployment of US strategic assets on the divided Korean peninsula, but declined to give further details. After North Korea last tested a nuclear device, in 2013, Washington sent a pair of nuclear-capable B-2 stealth bombers on a sortie over South Korea in a show of force.

At the time, North Korea responded by threatening a nuclear strike on the United States.

South Korea, technically in a state of war against the North, said it was not considering a nuclear deterrent of its own, despite calls from ruling party leaders. The United States is highly unlikely to restore the tactical nuclear missiles it removed from South Korea in 1991, experts said.

The United States is also limited in its military response for fear of provoking an unpredictable regime in Pyongyang, said Anthony Cordesman, a defense policy expert at the Washington-based Center for Strategic and International Studies think tank.

"Any escalation in this region, any over-reaction can easily lead to not only a conflict between South and North Korea, but drag China and the United States and Japan into a confrontation," as well, Cordesman said.

Hours after the latest nuclear test Wednesday, the U.N. Security Council said it would work immediately on significant new measures against North Korea. Diplomats said that could mean an expansion of sanctions against Pyongyang, although major powers might baulk at an all-out economic offensive.

North Korea also said it was capable of miniaturizing the H-bomb, in theory allowing it to be placed on a missile and potentially posing a new threat to the US West Coast, South Korea and Japan.

The impoverished state boasts of its military might to project strength globally but also plays up the need to defend itself from external threats as a way to maintain control domestically.

Hydrogen bombs use a two-step process of fission and fusion that releases substantially more energy than an atomic bomb. However, it will likely take several days to determine more precisely what kind of device Pyongyang set off as a variety of sensors, including "sniffer planes", collect evidence.

The size of the latest explosion was roughly consistent with previous tests and occurred in the same location as earlier tests.