Donald Trump has claimed credit for renewed dialogue between North and South Korea, saying US threats of nuclear war had pushed Pyongyang to re-establish contact with Seoul.

On Wednesday, the North reopened a border hotline that had been dormant for two years, suggesting a tentative thaw in relations at a time of heightened tensions on the Korean peninsula.

The move followed soon after the US President taunted his North Korean counterpart, Kim Jong-un, about the size of his "nuclear button".

Responding to the prospect of improved relations between Pyongyang and Seoul, Mr Trump said in a tweet on Thursday morning that the threat of an attack by the US had been decisive.

"Does anybody really believe that talks and dialogue would be going on between North and South Korea right now if I wasn’t firm, strong and willing to commit our total 'might' against the North," he said, adding that those who doubted him were "fools".

He also said talks between the historic enemies, who are still technically at war because the 1950-53 Korean War ended in a truce, not a peace treaty, were a "good thing".

Those remarks contradicted America's ambassador to the UN, Nikki Haley, who earlier this week sought to distance herself from the proposed contact.

“We don’t think we need a Band-Aid, and we don’t think we need to smile and take a picture. We think that we need to have them stop nuclear weapons, and they need to stop it now," she said.

South Korea offers to hold talks with North on Olympic cooperation

The US State Department warned the proposal could be an attempt to "drive a wedge" between Washington and Seoul.

The call lasted roughly 20 minutes but its contents were not made public.

North Korea shut down the hotline in retaliation for the closing of a border factory town jointly operated by the two Koreas.

North Korea's KCNA news agency quoted Ri Son Gwon, chairman of North Korea's Committee for the Peaceful Reunification of the Fatherland, as saying the talks would aim to establish formal dialogue about sending a North Korean delegation to the Olympics.

"We will try to keep close communications with the south Korean side from sincere stand(sic) and honest attitude, true to the intention of our supreme leadership, and deal with the practical matters related to the dispatch of our delegation," he said.

North Korea announces intercontinental missile launch Show all 13 1 /13 North Korea announces intercontinental missile launch North Korea announces intercontinental missile launch Pyongyang residents react after the news of the successful launch of the new intercontinental ballistic missile AFP/Getty Images North Korea announces intercontinental missile launch North Korea's leader Kim Jong Un signing an order to test-fire the newly developed inter-continental ballistic missile KRT via AP Video North Korea announces intercontinental missile launch A news broadcast displays Kim Jong Un's signed document AP North Korea announces intercontinental missile launch People cheer as they watch the news broadcast announcing Kim Jong Un's order to test-fire the new inter-continental ballistic missile AFP/Getty Images North Korea announces intercontinental missile launch Residents react after the document signing AP North Korea announces intercontinental missile launch Pyongyang residents celebrate Kim Jong Un's announcement AFP/Getty North Korea announces intercontinental missile launch Cheering Pyongyang residents react AP North Korea announces intercontinental missile launch To counter North Korea's missile test, South Korea fired missiles into the East Sea The Defence Ministry/Yonhap via REUTERS North Korea announces intercontinental missile launch The Hyunmu-2 missiles firing during the drill South Korean Defense Ministry vi North Korea announces intercontinental missile launch The exercise was carried out in an attempt to counter Kim Jong Un's order South Korea Defense Ministry via AP North Korea announces intercontinental missile launch The South Korean army continue to carry out military exercises AP North Korea announces intercontinental missile launch Where K-9 self-propelled howitzers were taking part in a drill Rex Features North Korea announces intercontinental missile launch US soldiers are also present in the border city of Paju AFP/Getty Images

In his New Year address, Mr Kim said he was willing to send a delegation to February's Winter Olympics, across the border in Pyeongchang.

But he also said he had a "nuclear button" on his desk and that the US mainland was within reach of his expanding weapons programme.