Kim Jong Un became the first head of state to grab President-elect Donald Trump's attention in 2017, after the North Korean leader said he was close to test-firing a missile capable of hitting the continental US.
"It won't happen!" Trump retorted on Tuesday on Twitter, a platform he frequently uses to weigh in on global and domestic affairs.
Still, Trump gave no specifics on how he'd actually do that.
Presidents from Bill Clinton to George Bush snr to Barack Obama have failed to stop North Korea moving closer to gaining the capability to strike the US with a nuclear weapon. That leaves the incoming president facing what is potentially the biggest challenge yet from the reclusive regime in Pyongyang.
"Trump has yet to look deeply into the North Korean conundrum, and when he does he'll realise there are only two choices: hit them or talk to them," said Park Hwee Rhak, head of the Graduate School of Politics and Leadership at Seoul's Kookmin University.
"No matter what you do, Kim will never give up his nuclear missile development. Thinking otherwise is belying reality."
Here are four options that Trump may consider to make good on his statement.
1 Military strike:
In 1994, the US deployed an aircraft carrier for a potential strike on North Korea's nuclear compound, according to a memoir published in 2000 by former South Korean President Kim Young Sam. The crisis ended after talks between ex-President Jimmy Carter and North Korean founder Kim Il Sung.
The costs of a strike would be higher now. North Korea's arsenal has grown with five nuclear tests since 2006. A surgical attack risks provoking a full-fledged war that could kill millions of people on the peninsula - including in South Korea, a key American ally.
Still, the idea of striking North Korea first has gained traction in South Korea in recent years. The nation is spending billions of dollars to buy weapons, including F-35 fighters, that would allow its military to conduct a first strike should Kim's regime show signs of an imminent nuclear launch.
The last six-nation nuclear talks with North Korea - a process that included the US - were held in 2008, and have been stalled since. The current US administration insists Kim agree to denuclearisation as a condition for talks to even be held. But Pyongyang has enshrined its nuclear arms in the constitution, and Kim has said the programme isn't up for negotiation.
Trump, a real estate billionaire who authored The Art of the Deal, said during his campaign he could negotiate directly with Kim over a hamburger to end his nuclear ambitions. But he's also likened Kim to a "maniac" and said he would get China to "make that guy disappear in one form or another".
"Trump touts himself as the master of deals," said Yang Moo Jin, a professor at the University of North Korean Studies in Seoul. "He'll try to talk first, and when he does he should make sure North Korea understands the military consequences of violating an agreement."
3 Missile defence:
President Park Geun Hye gave the US permission to deploy a high-altitude missile defence system known as Thaad on her country's soil after North Korea conducted its fourth nuclear test in January last year. Once installed, Thaad would join a network of American missile defence systems across the Pacific that aim to stop North Korean missiles reaching the continental US.
The Pentagon has said previously it plans to next test its ground-based system to destroy missiles aimed at the US in the first quarter of this year. A spokesman for the Missile Defence Agency said in September it has "demonstrated partial capability" against "small numbers of simple ballistic missile threats launched from North Korea and Iran".
That same month, Director of National Intelligence James Clapper told an audience in Washington that policymakers must assume that North Korea is able to hit the US with a nuclear-armed missile.
The US has a "layered" missile defence system to deter North Korea, Pentagon spokesman Peter Cook told reporters yesterday. He declined to say if the US would shoot down a North Korean missile, and would not discuss if its West Coast system would be effective against an intercontinental ballistic missile.
Trump may lean more on China, which provides most of North Korea's energy and food, to push Kim to abandon his nuclear programme and missile tests. The President-elect said in another tweet this week that China "won't help with North Korea" even though it "has been taking out massive amounts of money and wealth from the US".
But so far, Beijing's denouncements of North Korea's nuclear programme have had little impact. Kim's comment on the inter-continental ballistic missile came after China agreed in November to United Nations sanctions that included cutting North Korea's coal exports, one of the few sources of hard currency for his regime.