US President Donald Trump said he would be willing to talk to North Korean leader Kim Jong-un on the phone, but not without conditions.

"I always believe in talking," Trump briefly told reporters on Saturday.

"Absolutely, I would do that," he said when asked if he would be willing to talk to the North Korean leader.

Trump also said he hoped the upcoming talks between North and South Korea on Pyongyang's participation in the 2018 Winter Olympics would ease tensions over the North Korea's missiles and nuclear programme.

The high-level talks, to be held on January 9, will be the first such communications in more than two years.

Trump said he "very much" wants to see "it work out between the two countries," and took credit for the rapprochement.

"Without my rhetoric and tough stance," he said, "they wouldn't be talking".

The US president and the North Korean leader have repeatedly traded barbs in the past - Trump has called Kim "rocket man", while Kim described Trump as a "dotard".

Earlier this week, Trump responded furiously to Kim's taunt of a nuclear button, by saying his button was "bigger and more powerful".

The offer for talks on Olympic cooperation also came after South Korea and the US announced they would postpone joint military exercises that rile North Korea. Pyongyang says the war games held multiple times each year are a precursor to an American-led invasion.

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Trump described the inter-Korean dialogue as a "big start".

"If something can happen and something can come out of those talks, that would be a great thing for all of humanity, that would be a great thing for the world," he said.

South Korea's Yonhap news agency said on Sunday that North Korea's five-member delegation to the talks will be led by Ri Son Gwon, head of the Committee for the Peaceful Reunification of the Fatherland.

Cho Myoung-gyon, South Korea's unification minister, will head the delegation from Seoul.

The talks are to be held in the border village of Panmunjom.