South Korea has warned North Korea that using its nuclear weapons would put it on a "path of self-destruction," in unusually harsh language.
The warning came days after North Korea legislated a new law that would allow it to use its nuclear weapons preemptively.
North Korea will likely be infuriated by the South Korean rhetoric as Seoul typically shuns such strong words to avoid raising tensions on the Korean Peninsula.
Despite North Korea's increasingly aggressive nuclear doctrine, some experts say the country -- outgunned by more superior US and South Korean forces -- will still unlikely use its nuclear weapons first.
South Korea's Defence Ministry said the legislation would only deepen North Korea's isolation and prompt Seoul and Washington to "further strengthen their deterrence and reaction capacities."
To deter North Korea from using its nuclear weapons, the ministry said South Korea will sharply boost its own preemptive attack plan, missile defence and massive retaliation capacities while seeking a greater US security commitment to defend its ally with all available means, including nuclear one.
"We warn that the North Korean government would face the overwhelming response by the South Korea-US military alliance and go on the path of self-destruction, if it attempts to use nuclear weapons," Moon Hong Sik, an acting ministry spokesperson, told reporters.
White House press secretary Karine Jean-Pierre earlier said the United States "remains fully committed to the defence of (South Korea), using the full range of defence capabilities."
Jean-Pierre said the United States has no hostile intent toward North Korea and that it remains focused on pursuing close coordination with its allies to advance a shared objective of the complete denuclearisation of the Korean Peninsula.
Last week, North Korea's rubber-stamp parliament adopted the legislation on the rules for the use of its nuclear arsenal. It would allow the use of nuclear weapons if its leadership faced an imminent attack or if it aims to prevent an unspecified "catastrophic crisis" to its people.
The loose wording raised concerns the rules are largely meant as a legal basis for a preemptive nuclear strike to intimidate rivals into making concessions amid long-stalled negotiations over its arsenal.
Some experts say the North Korean move is also designed to strengthen the control of Kim Jong-un's leadership in the face of hardships caused by the pandemic and border closures.
During the parliament's meeting, Kim said in a speech that his country will never abandon its nuclear weapons to cope with US threats. He accused the United States of pushing to weaken the North's defenses and eventually collapse his government.
This year, Kim has dialed up weapons tests to a record pace by test-launching a slew of nuclear-capable ballistic missiles targeting both the US mainland and South Korea.
Since taking office in May, South Korea's new conservative government, led by President Yoon Suk Yeol, has said it would take a tougher stance on North Korean provocation but also offered massive support plans if the North denuclearises. North Korea has bluntly rejected that aid-for-disarmament.