US President Donald Trump has issued a blunt warning to North Korea's leader Kim Jong-un in an address to South Korea's parliament.
"Do not underestimate us. Do not try us," he said, while also condemning the "dark fantasy" of life in the North.
He addressed Mr Kim saying "the weapons you are acquiring are not making you safer", and urged other nations to join forces to stop Pyongyang.
The US leader is in South Korea as part of a five-nation tour of Asia.
Pyongyang's nuclear ambitions have been high on Mr Trump's agenda throughout this trip. Over the past year North Korea has carried out missile tests in defiance of UN sanctions and in September conducted its sixth and biggest nuclear test.
Mr Trump's words to South Korean lawmakers were being closely watched and while his rhetoric was stark, he did not repeat his previous bombast towards the North.
Trump made a personal address to Kim Jong-un
In an unexpected move, Mr Trump chose to directly address North Korea's leader in his speech, urging him to discard his nuclear programme and weapons.
"They are putting your regime in grave danger," warned Mr Trump. "Every step you take down this dark path increases the peril you face."
He also made reference to North Korea's founder and Mr Kim's grandfather, Kim Il-sung, in words likely to inflame Pyongyang.
"North Korea is not the paradise your grandfather envisioned. It is a hell that no person deserves."
But Mr Trump also appeared to reiterate Tuesday's offer to reach a deal, saying that "despite every crime you've committed... we will offer you a path for a better future".
He warned the North against 'fatal miscalculation'
He said that to interpret past US restraint as weakness "would be a fatal miscalculation", as there was now a different US administration in place.
"Today, I hope I speak not only for our countries but for all civilised nations, when I say to the North: 'Do not underestimate us. Do not try us'."
He pointed to the heavy US military presence in the Korean peninsula including aircraft carriers and fighter jets, saying: "I want peace through strength."
But he also made sure to single out North Korea's biggest economic supporter, China, as well as Russia, calling on them to sever all ties including economic ones.
Earlier on Wednesday, Mr Trump was forced to drop a surprise visit to the demilitarised zone (DMZ) between North and South Korea due to bad weather.
The US President is travelling to China on Wednesday, and will also be visiting Vietnam and the Philippines this week.