Republican presidential candidate Donald Trump at a campaign rally at the USS Wisconsin battleship in Norfolk, Virginia, on October 31. REUTERS/Joshua Roberts GOP frontrunner Donald Trump recently suggested that if he won the US presidency, he might allow Japan and South Korea to develop their own nuclear weapons arsenal in exchange for an ease in US defense commitments.

But experts from two nonpartisan organizations opposed to the spread of nuclear weapons told Business Insider his position would be dangerous.

Jeffrey Lewis, the director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies, said Japan building nuclear weapons would be a "total catastrophe for Japan and US nuclear power programs."

"Early on we thought nuclear weapons are great when our allies have them and bad when our enemies have them," Lewis said.

He went on to say how that thinking had evolved:

Everybody has a friend. And so if you can give them the path of saying it's good when our allies have them and bad when our enemies have them, you get to the point where everybody has them. It's better to have a system … in which we say no more nuclear-weapons states and try to maintain that.

Japan and South Korea obtaining nuclear weapons could have a domino effect as other countries, including some US allies in the Middle East, demand their own arsenal.

"A large number of our other allies would want the same treatment immediately," Lewis said. "Probably lots of Middle Eastern states. I think you would get a lot of countries wanting nuclear weapons."

Kingston Reif, the director for disarmament and threat-reduction policy at the Arms Control Association, made a similar point.

"If South Korea and Japan were to acquire their own nuclear deterrents, that would send an incredibly dangerous signal to our allies in the Middle East," he told Business Insider. "It would be incredibly destabilizing development," he added.

Trump explained his stance on expanding the number of nuclear powers in a New York Times interview that was published over the weekend. The Republican presidential frontrunner said that "at some point" the US "cannot be the policeman of the world," referring to its commitments to contribute to the defense of its allies.

He said that while he thought the "biggest problem" in the world was nuclear proliferation, he might be open to allowing Japan and South Korea to have their own nuclear arsenals in exchange for a decrease in contributions to their defense by the US. Both countries are threatened by North Korea, a dictatorship that has been developing nuclear capabilities.

Dylan Roach/Business Insider "Would I rather have North Korea have [nuclear weapons] with Japan sitting there having them also?" Trump told The Times. "You may very well be better off if that's the case. In other words, where Japan is defending itself against North Korea, which is a real problem. You very well may have a better case right there."

Reif called this stance "irresponsible."

"The US needs to be playing an even more active role than it is currently playing in reducing nuclear buildup, and Trump's comments will not make that job any easier," Reif said.

And Trump's potential plan wouldn't be likely to accomplish much. Reif pointed out that India's and Pakistan's possession of nukes hadn't stopped the aggression between them. And Israel's arsenal hasn't stopped it from being threatened.

So even as North Korea poses a nuclear threat, it's unlikely that additional nukes in surrounding countries will ease tensions.

"This idea that this would bring more security to Japan and South Korea than the US troops deployed there and the US defense commitment to those countries is not borne out by the evidence," Reif said.

Lewis said Trump's plan "would sound half-clever if he was sitting on a bar stool."

"We tried to let the Japanese defend themselves at one point," Lewis said. "It did not go well."

He noted that even if the US were to allow Japan to build nuclear weapons, it's unlikely the country would want to.

This was affirmed by the Japanese government on Monday. The country's chief cabinet secretary, Yoshihide Suga, told reporters that Japan's commitment to not owning, making, or allowing nuclear weapons "remain an important basic policy of the government," according to the Associated Press.

But South Korea might be a different story. Polls show that there has been growing public support in the country for establishing an independent nuclear arsenal. If South Korea were to revise its position on nonproliferation, it could have far-reaching consequences.

"This would further reduce the likelihood of achieving a nuclear-free Korean peninsula," Reif said. "Right now that prospect seems pretty distant, but it would likely be closed off for good if South Korea were to get its own deterrent."

Aside from the Korean peninsula and the Middle East, China might also look to get more even more nuclear weapons if there were a buildup in South Korea and Japan.

Military delegates arriving for a meeting ahead of the opening ceremony of the National People's Congress in Beijing on March 4. REUTERS/Jason Lee

China's "doctrine regarding when it might employ nuclear weapons might be described as one of minimum deterrence," Reif said. "China right now is believed to have no more than 300 total nuclear weapons, which is a small arsenal relative to what the US and Russia possess."

He continued:

But in the event that South Korea and Japan acquire independent nuclear weapons, it's highly likely that China would revisit its minimum deterrence posture and likely accelerate its ongoing nuclear modernization efforts and consider increasing the overall size of its nuclear arsenal.

Lewis further cautioned that having several nuclear-weapons states in Northeast Asia could be dangerous.

"It would be a free-for-all," he said. "It would be a giant science experiment that I would not want to see."

The US might also expect to see a conventional military buildup from China if other countries in the region were to obtain nukes, Reif said.

The US is already contending with China's military buildup in the South China Sea, where China is laying claim to strategically significant island chains. The country wants to build military outposts on the islands that would give it greater control of the waters surrounding the mainland.

"If we think that the military buildup in the region is concerning now, just wait to see what happens in the event that South Korea or Japan get their own nuclear deterrents," Reif said. "That's likely to increase the threat that China poses to the US and its allies in the region."