US and North Korean officials have held secret contacts recently in which Pyongyang directly confirmed its willingness to hold the unprecedented summit, the official told Reuters, speaking on condition of anonymity.
North Korea is reportedly advocating for the summit to be in Pyongyang, while the capital of Mongolia is also under consideration.
According to the report, American officials are said to have spoken several times with their North Korean counterparts, and even met up with them up to three times to discuss preparations.
As recently as this weekend, Trump told associates he was looking forward to the summit, which he agreed to on the spot when presented the invitation from Kim.More news: United States crude oil inventories decrease in past week
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CNN reported on Saturday that the USA and North Korea have been holding secret, direct talks to prepare for the summit. Last month, a New York Times report said that the Central Intelligence Agency was taking the lead in preparing for the Trump-Kim summit.
But Pyongyang has been silent publicly since then about a summit, even as Kim visited Beijing earlier this month in his first visit outside North Korea since assuming control of the country after his father, Kim Jong-il, died in 2011.
"Even if we were aware of the talks, we can not comment on it", said an anonymous Cheong Wad Dae official, according to Yonhap News Agency. South Korea's National Intelligence Service Chief Suh Hoon has been in close contact with his USA and North Korean counterparts.
Mr Trump said: "We're moving along very nicely with North Korea".
The United States responded by frequently sending its strategic assets such as long-range bombers and aircraft carriers to the region in a show of force and floating talks of military options against North Korea. The Koreas have to also decide how many times Kim and Moon would meet on April 27 and whether parts of the summit would be broadcast on live television.