Kim Jong Un warned the United States on Monday that North Korea would be ready to strike if it felt threatened, while striking a more conciliatory tone towards the South.
During his customary annual address, he said that Washington must accept the fact that North Korea was now a nuclear power and not a threat.
He declared that his country had achieved the historic feat of "completing" its nuclear forces and added that he has a nuclear button on his desk.
"The US should know that the button for nuclear weapons is on my table," he said during the speech, as provisionally translated by The Associated Press.
"The entire area of the US mainland is within our nuclear strike range. ... The United States can never start a war against me and our country," Kim said.
He also called for improved relations with the South, an idea mentioned in speeches more often than it is met. He said the Pyeongchang Winter Olympics set for February would be a good opportunity to showcase the status of the Korean nation.
He also said the two Koreas could meet urgently to discuss the North sending a delegation.
"The Winter Olympic games that will be held soon in the South will be a good opportunity to display the status of the Korean nation and we sincerely wish that the event will be held with good results," he said.
“When it comes to North-South relations, we should lower the military tensions on the Korean Peninsula to create a peaceful environment,” Kim said. “Both the North and the South should make efforts.”
Kim said he will consider sending a delegation to the Winter Olympics Games.
South Korea's presidential office said it welcomed the proposal to hold talks between government officials over the issue of North Korea sending a delegation to the Olympics.
The office of President Moon Jae-in said the successful hosting of the Pyeongchang Olympics would contribute to peace and harmony not only on the Korean Peninsula and in Northeast Asia, but in the entire world.
“We have always stated our willingness to talk with North Korea any time and anywhere if that would help restore inter-Korean relations and lead to peace on the Korean peninsula,” a spokesman for the presidential Blue House said.
The New Year's address is an annual event in North Korea and is watched closely for indications of the direction and priorities Kim may adopt in the year ahead.
This year's speech was seen as particularly important because of the high tensions over Pyongyang's frequent missile launches and its nuclear test in 2017.
The tests were the focus of fiery verbal exchanges between North Korea and President Donald Trump, who has derisively called Kim "little rocket man."
Kim also stressed North Korea's economic achievements during the speech, and noted the importance of improving the nation's standard of living.