Opposition parties and sections of South Korea's media are stepping up calls for the government to invite the United States to reintroduce tactical nuclear weapons to the country as Pyongyang is showing no signs of halting its development of nuclear weapons and intercontinental ballistic missiles.

The US withdrew its battlefield nuclear weapons from South Korea in the early 1990s under an agreement reached between Seoul and Pyongyang to build better relations and a nuclear-free Korean Peninsula. Despite that agreement, the North pushed ahead with the development of a nuclear arsenal and carried out its first underground nuclear test in October 2006.

To date, North Korea has conducted seven nuclear tests, with the explosion at its Punggye-ri proving grounds on Sunday estimated to have had a yield of 120 kilotons. In comparison, the weapon that devastated Hiroshima in 1945, which killed around 130,000 people, had a yield of 15 kilotons.

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Additional deterrent

The head of the Liberty Korea Party on Tuesday called on the government of Moon Jae-in to ask Washington to bring back tactical nuclear weapons as an additional deterrent to the North.

"Whether Washington is willing to redeploy part of its tactical nuclear force to Korea is a matter of whether the US has the will to protect the Republic of Korea with its nuclear umbrella," Hong Joon-pyo said.

"To test the US' nuclear umbrella policy, we have to call for redeployment," Yonhap News quoted Hong as saying.

The hawkish Hoon also pointed out that Washington has around 160 theater tactical missiles in Europe and another 150 units in the continental US.

Song Young-moo, the defense minister, indicated in parliamentary hearings on Monday that he was "willing to consider" asking the US to return nuclear weapons to the South, although that would run counter to the administration's commitment to eliminating nuclear weapons from the peninsula.

Conservative media outlets support Hoon's position, with the Chosun Ilbo newspaper running an editorial in Tuesday's edition headlined "Nuclear option can no longer be taboo for South Korea."

The editorial stated that Kim Jong Un, the North Korean dictator, "Will never give up its nuclear weapons," while diplomatic options have effectively been exhausted and China and Russia continue to tacitly support Pyongyang.

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Previously taboo

"At a time when the entire security landscape has shifted, options must be considered that have so far been taboo," the paper stated. "A nuclear threat must be met with a nuclear deterrent. There is no other option."

The editorial suggested that a debate needs to be held on South Korea developing and deploying its own independent nuclear capability but, in the meantime, that the US bring tactical nuclear weapons back to the peninsula.

Ahn Yin-hay, a professor of international relations at Korea University, believes that as Pyongyang shows no sign of complying with international requests to halt its missile and weapons programs, the Moon administration will come under increasing pressure to do more to protect the South Korean public.

"We have learned that the only way to deter the North from upsetting the balance of power is by having a nuclear capability, so it is something that at least has to be considered," Ahn told DW.

"If North Korea continues to improve its nuclear capability then there is no possible way out for the South, and that is extremely worrying," she said.

President Moon has already mentioned the "red line" that North Korea has crossed with its weapons development, Ahn pointed out, so he is responsible for making sure that the North understands that those actions have consequences.

"I do not think it is possible for the opposition to convince the country to withdraw from the Nuclear Non-Proliferation Treaty and for us become a nuclear power in our own right - that would be too difficult - but it would be far easier to deploy US tactical nuclear weapons."

"And with the public becoming increasingly fearful and the opposition pushing, there is going to be a lot of pressure on Moon to do that," she added.

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Reversing course

James Brown, an associate professor of international relations at the Tokyo campus of Temple University, agrees that Moon has moved away from some of his earlier commitments on security, such as permitting the deployment of the US Army's Terminal High Altitude Area Defense (THAAD) anti-missile system, but believes there is little value in reintroducing nuclear weapons to the South.

"Agreeing to the deployment of tactical nuclear weapons in the South would be on a different level entirely to THAAD and I think Moon would be very reluctant to take that step," he said.

"It would primarily be a political symbol because nuclear weapons in the South would not change the military situation on the peninsula," he said. "The South does not need to have these weapons because they, combined with the US, have an advantage over the North in terms of conventional weaponry, there is no doubt who would win the war."

"What they need to do is to show that capability off to the North, which they have been doing in recent weeks, and I expect to see a lot more of that," Brown said.