North Korean leader Kim Jong-un has renewed his commitment to denuclearisation but warned that he may have no option but to seek an alternative course if the United States does not take corresponding measures and maintains sanctions.

Kim made the comments on Tuesday during his annual New Year's Day address, laying out Pyongyang's top priorities for the 12 months ahead.

In a 30-minute speech broadcast by North Korea's state television, he said there would be faster progress on denuclearisation if Washington took the corresponding action.

North Korea would have "no option but to explore a new path in order to protect our sovereignty" if the US "miscalculates our people's patience, forces something upon us and pursues sanctions and pressure without keeping a promise it made in front of the world", Kim said.

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He was referring to his landmark summit with US President Donald Trump in Singapore in June, when he said he had "fruitful talks" and "exchanged constructive ideas".

At the time, the two leaders signed a vaguely-worded pledge on denuclearisation of the Korean Peninsula, but progress has since stalled with Pyongyang and Washington arguing over their agreement's interpretation.

"I am ready to sit with the US president again at any time in the future and will make efforts by all means to produce a result that will be welcomed by the international community," Kim said.

Al Jazeera's Rob McBride, reporting from the South Korean capital, Seoul, said Kim's address was markedly different compared with previous ones in both content and style.

"Gone was the imposing podium of previous years, it was more like a fireside chat from a warm study overlooked by portraits of his father and grandfather," said McBride.

"A year ago, he spoke about nuclear weapons almost in terms of bragging - that North Korea had now achieved the possession of a nuclear arsenal. This time, he made a very different pledge about nuclear weapons, saying that North Korea is committed to peace and denuclearisation, making a pledge that weapons would not be used, they are not being tested and the nuclear technology is not being spread or proliferated."

Pyongyang has demanded Washington lift sanctions and declares an official end to the 1950-1953 Korean War in response to its initial, unilateral steps towards denuclearisation, including dismantling its only known nuclear testing site and a key missile engine facility. The North is also subject to multiple sets of United Nations Security Council sanctions over its nuclear and ballistic missile weapons programmes.

Kim spent more than 20 minutes of his speech talking about North Korea's economy, saying that improving people's lives was his top priority and tackling energy shortages was an urgent task.

He also called for South Korea to stop joint military exercises with "outside forces" involving strategic assets, calling such drills a "source of tension". "War-related equipment - including strategic assets of outside powers - should no longer be allowed to be brought in," he added.

Seoul and Washington are in a security alliance and the US stations 28,500 troops in the South.

But relations between North and South Koreas saw a major thaw in 2018.

With three leaders' summits in 2018 and dozens of other meetings, the Koreas have opened a liaison office in the North Korean border town of Kaesong, created border buffers and no-fly zones to reduce military tensions, and jointly surveyed North Korea's outdated railways and roads with the goal of connecting them with the South.

Calling for stronger inter-Korean cooperation, Kim said the North is ready to resume operations at a jointly run factory park in Kaesong and restart South Korean tours to the North's Diamond Mountain resort. Neither of those is possible for South Korea unless sanctions are removed.

"Kim spoke about 2018 being a momentous year and he said he wants to carry forward this momentum into 2019," said McBride, adding that the focus now is on whether the North Korean leader will make a long-awaited and historic visit to the South in the new year.