Kim Jong-un used a New Year's Day speech to warn the United States that he was now able to hit all of the US mainland with his country's nuclear weapons.
He said North Korea would spend 2018 mass producing nuclear warheads and ballistic missiles, and that the US would never be able to start a war against them.
"The entire United States is within range of our nuclear weapons, and a nuclear button is always on my desk," he said during the televised address.
"This is reality, not a threat."
But Kim also called for reduced military tensions on the Korean peninsula in what appeared to be an olive branch to South Korea.
The North Korean leader said he was open to dialogue and would consider sending a delegation to the Winter Olympic Games that the south is hosting in the city of Pyeongchang in February.
"North Korea's participation in the Winter Games will be a good opportunity to show unity of the people and we wish the Games will be a success," Kim said.
"Officials from the two Koreas may urgently meet to discuss the possibility."
South Korea said it welcomed Kim's offer to send a delegation to the Pyeongchang Games and hold talks with the South to discuss possible participation.
"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.