LONDON • United States President Donald Trump is "a tough dealer" who has extensive dealmaking experiences, said South Korean Prime Minister Lee Nak Yon.

"President Trump has a sixth sense. He must have gone through a number of things from dealmaking experiences. The closest thing to describe him would be a tough dealer," Mr Lee said on Sunday during a meeting in London with reporters travelling with him on a European trip, South Korea's Yonhap news agency reported.

Mr Lee also said he believes the US-North Korea summit will take place as planned on June 12 in Singapore as both Mr Trump and North Korean leader Kim Jong Un "share political risks" from the meeting falling apart.

It has been a roller-coaster ride since it was announced in March that Mr Trump and Mr Kim would meet.

The twists and turns so far included North Korea suddenly stepping up criticism of the United States, jeopardising weeks of diplomatic progress by saying it may reconsider the June 12 summit.

North Korea on May 16 threatened to scrap the summit if Pyongyang was pushed towards "unilateral nuclear abandonment".

Then last Thursday, Mr Trump abruptly announced in a personal letter to Mr Kim that he was cancelling their meeting. The US leader blamed open hostility from North Korea for his decision, and warned Pyongyang against committing any "foolish or reckless acts".

Some say his sudden willingness to walk rattled Pyongyang, which has since dialled down its rhetoric and expressed a willingness to talk "at any time".

"Trump's unexpected response totally took Kim by surprise and left the North scrambling to find a way to mend things," Mr Cho Sung Ryul, a senior researcher at the Institute for National Security Strategy, told Agence France-Presse.

Others say that the crisis was primarily averted by Mr Kim and South Korean President Moon Jae In, who made the extraordinary decision to hold an impromptu meeting on North Korea's side of the Panmunjom truce village between the two Koreas last Saturday.

The two leaders agreed during two-hour talks that a North Korea-US summit must be held.

Asked if Mr Moon will also travel to Singapore for the US-North Korea summit, Mr Lee said that discussions between Mr Trump and Mr Kim are not expected to go as far as talking about formally ending the 1950-1953 Korean War.

Any peace treaty or agreement to formally end the war will have to involve North Korea, China and the United States, signatories of the armistice which brought about a ceasefire in 1953.

That means Mr Moon is unlikely to travel to Singapore, Yonhap reported.