WASHINGTON – The younger sister of North Korea’s leader is threatening nuclear war against South Korea in remarkably florid language clearly intended to intimidate the incoming conservative government of the South’s president-elect, Yoon Suk-yeol.

Kim Yo-jong declared Tuesday that the North’s nuclear combat force “will have to inevitably carry out its duty” in response to “military confrontation” by South Korea. She was responding to a recent remark by South Korea’s defense minister, Suh Wook, that his country’s forces could “accurately and swiftly” attack the sites from which the North has been test-firing missiles.

Her brother, Kim Jong-un, has often had her making threats that he would prefer not to issue in his own name.

It’s difficult to imagine North Korea actually opening a nuclear war against South Korea, but the nature of the rhetoric shows a rising level of North-South animosity that’s likely to intensify after Mr. Yoon takes office next month. Her emphasis on nuclear strength also suggested her brother might order a seventh underground nuclear test; the North conducted the last in September 2017.

Kim Yo-jong could, of course, have said North Korea could counter South Korean missiles with its own more powerful missiles. She preferred, however, to let the world know, in a dispatch carried in English by Pyongyang’s Korean Central News Agency, that North Korea as a nuclear power would not hesitate to unleash its nukes against enemies near and far, including the U.S.

“It is the primary mission of the nuclear forces to prevent such a war first of all,” she said, “but in case of war, its mission will convert into the one of eliminating the enemy’s armed forces at a strike.”

Indeed, she went on, “A nuclear combat force is mobilized to take the initiative at the outset of war, completely dampen the enemy’s war spirits, prevent protracted hostilities and preserve one’s own military force.”

As a result, she said, “a dreadful attack will be launched” and the South Korean army “will have to face a miserable fate little short of total destruction and ruin.”

The statement also appeared in Korean in Rodong Sinmun, the authoritative newspaper of the ruling Workers’ Party, which indicated that Kim Yo-jong and her brother were also anxious to impress their own people of their power and will to defeat the South.

Daily NK, a website in Seoul that’s in touch with sources in North Korea through risky cellphone contacts, reports that residents in the northern reaches of the country “have been less than enthusiastic about the launch” of North Korea’s latest missile, which the North proudly identified as a Hwasong-17 capable of striking almost anywhere on Earth.

“They say the authorities should first resolve the food shortages they currently face,” said Daily NK. Indeed, “locals complain that even though more and more families are running short of food by the day with the start of spring, the authorities have not found a solution to the food shortages.”

Instead, said Daily NK, people up there complain they “fire tons of cash into the sky with missile launches.”

Against this background, Kim Yo-jong’s statement appeared as a rationale intended for domestic consumption for North Korea’s costly program for developing nuclear warheads and the missiles to carry them to distant targets.

Somewhat gratuitously, she insisted her warning was “not a threat” but rather “a detailed explanation of our reaction to possible reckless military action” by South Korea.

The notion of a “preemptive strike against a nuclear-armed state,” said Kim Yo-jong, in a swipe at South Korea’s defense minister, was “a fantastic daydream,” the “hysteria of a lunatic.”