Calls are growing for South Korea to seek the deployment of United States tactical nuclear weapons in the country, as a "fight nuclear with nuclear" debate was reignited after North Korea tested two intercontinental ballistic missiles last month.
South Korea's main opposition party has repeatedly urged the government on the nuclear deployment. Seoul has meanwhile embarked on talks with Washington to boost its missile defence against Pyongyang's provocations.
There is also talk among politicians and scholars for South Korea to develop its own nuclear programme, as doubts grow over US President Donald Trump's willingness to defend South Korea.
But analysts warn of serious ramifications for the country's longstanding security alliance with the US and its commitment to the Nuclear Non-Proliferation Treaty.
Dr Go Myong Hyun from The Asan Institute for Policy Studies said the most realistic way for South Korea to boost its nuclear power is through "very close coordination with the US", with joint control over US assets.
Citing the North, which faces international sanctions for its unilateral nuclear policy, he said: "Why would South Korea do that?"
Under their security alliance, the US provides South Korea - and Japan - with a nuclear umbrella against North Korean threats.
Seoul is already pushing to build more powerful missiles in talks with Washington. Pentagon spokesman Jeff Davis said on Monday that they are reviewing bilateral guidelines and would be "favourably inclined" to boost Seoul's defence capabilities.
South Korea is bound by guidelines - last amended in 2012 - to develop missiles with a maximum payload of 500kg and that can travel 800km. But this is now deemed insufficient.
South Korean President Moon Jae In, in a phone conversation with his US counterpart on Monday, raised the topic of developing nuclear submarines. Mr Moon's aide said the two leaders did not delve into details, but analysts still consider it a significant move by the pro-rapprochement President, who is under pressure to harden his stance against the North.
Pyongyang has so far ignored offers of dialogue and collaboration from Seoul. North Korean Foreign Minister Ri Yong Ho, in a brief chat with his South Korean counterpart Kang Kyung Wha in Manila, even said Seoul's dialogue offer "lacks sincerity".
Mr Moon's North Korea policy is "unrealistic", said opposition leader Hong Joon Pyo of the Liberty Korea Party, known for its hardline stance. He said peace can be achieved only through a balance of power, "not when we are begging for it". It is time, he said, for Seoul to engage Washington in "earnest discussions" about the redeployment of US tactical nuclear weapons meant for use on the battlefield. These were withdrawn in 1991 with the two Koreas signing a joint declaration against them.
North Korea expert Yun Duk Min, meanwhile, called for the deployment of strategic nuclear assets, such as a US submarine carrying nuclear weapons.
"Overwhelming deterrence, not diplomacy, is the only thing that can protect the South," Professor Yun from the Hankuk University of Foreign Studies wrote in a commentary in JoongAng Ilbo.
Other analysts warn of consequences, including objections from China, whose economic retaliation against the deployment of the US Terminal High Altitude Area Defence (Thaad) anti-missile system has hurt South Korea.
Dr Go said: "Thaad is a defensive system... Tactical nukes are offensive. Can you imagine the Chinese reaction?"