SEOUL—The United States should keep enhancing its nuclear deterrent in South Korea until North Korea gives up on its nuclear weapons program, a South Korean think tank researcher said.

Cha Du-hyeogn, a principal fellow at the Seoul-based Asan Institute for Policy Studies, said in an interview with The Asahi Shimbun that North Korea is increasingly and aggressively developing missiles and nuclear weapons.

He said he was engaged in a joint report with a U.S. research center that calls on the United States to offer a stronger assurance of its nuclear umbrella for Seoul.

The report, published in late October, suggests an option of four steps to redeploy U.S. tactical nuclear weapons to South Korea. Cha said using this option would send a message to Pyongyang.

Excerpts of the interview follow:

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Q: What is your assessment of North Korea’s nuclear weapons development?

Cha: Pyongyang produces a sufficient amount of nuclear material for weapons, allowing for the annual creation of 12 to 15 atomic bombs. It is projected to have 240 nuclear bombs by 2027 and 450 by the mid-2030s.

Both China and Russia are remaining silent over the issue, but they may step in when the North’s nuclear arsenal exceeds a certain level.

Q: What approach should be taken now? Would you explain the four steps for enhancing Washington’s nuclear deterrence presented in the report.

A: The first step (of building storage facilities in South Korea for U.S. tactical nuclear weapons) should already be under consideration.

There were such facilities in the South until Washington withdrew its tactical nuclear weapons from the Korean Peninsula in 1991. Those depots were specially designed to prevent radiation leaks and withstand enemies’ attacks.

Reinstalling the depots would help spread the message that the United States will “redeploy tactical nuclear weaponry on the Korean Peninsula at anytime in the event of an emergency.”

In the second step, some U.S. nuclear submarines operating in the Indo-Pacific area are expected to be assigned the task of retaliating against a North Korea nuclear attack.

At the Washington-Seoul summit in April this year, a message was released that “North Korea’s use of nuclear weapons would mean the collapse of the Kim Jong Un administration.” The second step would ensure concrete measures for this message.

As the third step, Seoul is supposed to cover the costs of modernizing Washington’s B61 nuclear bombs.

The fourth step (redeploying U.S. tactical nuclear weapons to South Korea) would lead to the permanent stationing of eight to 12 tactical nuclear weapons in the South.

The degree of North Korea’s nuclear development will determine which steps need to be implemented.

For example, all of the steps could be suspended if Pyongyang agrees to move its nuclear materials outside the nation.

Q: Could the proposed steps result in an arms race between the North and South?

A: These approaches do not represent nuclear proliferation. Washington’s arrangement and targeting of nuclear weapons will simply be changed.

From a historical standpoint, disarmament and arms control can never begin unless both parties feel threatened. Disarmament plans initiated by political motivation rather than military needs can easily go flat, like the 2018 military accord between the two Koreas.

Disarmament and arms control without mutual trust mean nothing. Irrelevant parties recklessly insist that what must be done is not military expansion but disarmament. However, disarmament can never succeed without a sense of urgency.

For North Korea, nuclear disarmament is possible only after the effects of economic sanctions emerge as a serious concern or when leader Kim Jong Un believes that using nuclear weapons will lead to retaliation with nuclear weapons.

The steps are intended to show a firm determination in getting Pyongyang to abandon its nuclear development program.

Q: What is your take on calls for nuclearization among South Koreans?

A: Behind the release of this report are growing concerns among South Koreans that Washington might not use nuclear bombs in retaliation for a nuclear attack against us.

Another message of this report is, “The United States has a method to eliminate Seoul’s worries without the nuclearization of South Korea.”

Conservatives and progressives (reformists) differ on the issue of nuclearizing South Korea.

The conservative faction wants to ramp up the U.S.-Seoul alliance, so owning nuclear weapons would not be among the options if that could destroy the alliance.

The progressive side believes that if both North and South have nuclear weapons, they can hold talks without outsiders’ interference. Progressives want to subsequently achieve independence from Washington.

Our survey reveals that 60 to 70 percent of South Koreans prefer nuclearization, too. But after considering that nuclearization would result in international sanctions, the ratio dropped to 50 percent or so.

When the price of nuclearization is taken into account, most people would think the redeployment of U.S. tactical nuclear weapons on the Korean Peninsula is more realistic.

Q: Do you expect Washington to respond positively to your calls for redeploying its tactical nuclear weapons?

A: I do not think the United States will readily accept the offer.

It should be noted that Washington 10 years earlier only stated “believe in our promises” and other such things.

The U.S. has lately started telling us that they “understand South Koreans’ concerns.” In April, they announced the U.S.-South Korea Washington Declaration to enhance extended deterrence under the U.S. nuclear umbrella.

The report this time would have been dismissed as “lacking feasibility” if it had been compiled 10 years ago.

The fact that it was presented with U.S. Rand Corp. has huge significance, I believe.

Q: What would you expect if Donald Trump were to win the U.S. presidential election next year?

A: Mr. Trump actually does not care about alliances with other nations. His inauguration would hurt not only U.S.-South Korea ties but also the relationships between Tokyo, Washington and Seoul.

However, about half of the diplomatic policies of the Biden administration were taken over from the Trump administration.

Trump is apt to prioritize economic benefits, so our third step--Seoul’s covering the cost of modernizing B61 nuclear bombs—would draw a positive response from him.