US President Donald Trump said that high-level talks have started between the US and Democratic People's Republic of Korea officials, and that he will probably meet the DPRK's leader Kim Jong-un in May or early June outside the US.

In his talks with visiting Japanese Prime Minister Shinzo Abe at his Mar-a-Lago retreat in Palm Beach, Florida on Tuesday, Trump also said he had given his blessing to the inter-Korean talks aimed at formally ending the Korean War.

"We have had direct talks at very high levels, extremely high levels, with North Korea (DPRK). I really believe there's a lot of good will; a lot of good things are happening."

Trump later clarified the talks by saying, "Let's leave it a little bit short of the highest level."

White House spokeswoman Sarah Sanders added: "The president said the administration has had talks at the highest levels and added that they were not with him directly."

US Secretary of State nominee and CIA Director Mike Pompeo made a secret visit to DPRK over the Easter weekend and met with Kim Jong-un, Reuters cited an unidentified senior US official as saying on Tuesday.

"The administration does not comment on the CIA director's travel," Sanders said.

Contacts between the two sides in recent weeks have involved US intelligence and State Department officials.

Trump said, "We'll be having meetings with Kim Jong-un very soon. It will be - that will be taking place probably in early June or a little before that - assuming things go well."

Trump said the US is weighing five different locations for the Trump-Kim summit, but none are located in the US. Trump, however, also said the summit might not happen.

"It's possible things won't go well and we won't have the meetings, and we'll just continue to go along this very strong path that we've taken," he said. "But we will see what happens."

Trump also said the two Koreas are "discussing an end to the war", and they have his blessing on that.

Reuters contributed to this story.