The United States should consider jointly handling nuclear weapons with South Korea and Japan so as to prevent the key Asian allies from seeking nuclear armament of their own, a U.S. expert has suggested.

Evan Braden Montgomery, a senior fellow at the Center for Strategic and Budgetary Assessments, put forward the "combined nuclear planning and nuclear sharing" idea in a recent report, saying the allies could consider independent nuclear armament if North Korea's nuclear capability surges.

"How might Washington prevent nuclear proliferation if South Korea were to decide that it needed to offset North Korea's nuclear arsenal, if Japan were to determine that it had no other option to balance against a rising China, or if both of these outcomes occurred?" Montgomery said in the report.

One possibility would be to establish mechanisms that are similar to those that can be found in Europe, including both "combined nuclear planning groups and nuclear sharing arrangements," he said.

"If Seoul and Tokyo had a clearer window into how the United States intended to conduct nuclear operations and a direct role in delivering nuclear weapons, at least under certain conditions, then both allies might be willing to forgo the alternative of indigenous nuclear weapons programs," he said.

The idea would be a major departure from the traditional U.S. approach to alliances in the Asia-Pacific, but is still better than watching the allies develop and field independent nuclear weapons, over which the U.S. would have no control, including when and how they might be used, he said.

Moreover, Japanese and South Korean nuclear arsenals that were untethered to the United States could end up being a major source of instability between these two nations, irrespective of their impact on North Korea and China, the expert said.

In addition, trilateral nuclear planning and sharing would provide a unique opportunity to transcend long-running tensions between South Korea and Japan and foster closer ties between the two historical rivals, he said.

A possible location for nuclear weapons to be jointly handled would be Guam, he said.

Unless these weapons are forward-based in or near the theater, they might not be particularly useful in a crisis or credible as deterrent, but forward-based weapons can be particularly vulnerable to attack, and the political complications of stationing them abroad could create even bigger problems, especially in Japan, he said.

"Therefore, one way to address these issues, and perhaps promote increased trilateral cooperation as well, would be to base nuclear weapons at a central and neutral location like the U.S. territory of Guam," the expert said.

"This would reduce their vulnerability, mitigate blowback in South Korea and Japan, and perhaps allow the three allies to coordinate and train with one another for the nuclear delivery mission," he said.

The North's fourth nuclear test in January and a long-range rocket launch the following month have rekindled calls in South Korea for nuclear armament, with some leading members of South Korea's ruling party arguing that it makes no sense to rely on the U.S. "nuclear umbrella" as the North's nuclear arsenal grows.

But the government has rejected the idea as running counter to the principle of a nuclear-free peninsula.

"If North Korea succeeds in building a nuclear arsenal that is large enough and secure enough to withstand an attack and conduct a reprisal, and especially if it gains the ability to launch nuclear weapons against U.S. territory, then policymakers in Seoul might begin to doubt whether the United States would really employ nuclear weapons on their nation's behalf," Montgomery said.

The countries might consider an independent nuclear capability as a helpful tool when it comes to managing lower-level provocations, he said.

"That is, if Pyongyang is willing to sink South Korean naval vessels or launch artillery strikes against inhabited islands because it has an escalation advantage on the Peninsula, Seoul might conclude that its own nuclear weapons would provide it with greater freedom to respond in kind and therefore might deter these types of attacks in the first place," he said. (Yonhap)