North Korea has offered to freeze its nuclear and missile programmes if the US begins direct talks on an agreement that would eventually see a nuclear free Korean peninsula.
He said Kim had said denuclearisation could be discussed in negotiations between North Korea and the United States.
US President Donald Trump welcomed Pyongyang's offer as positive and apparently sincere crediting Washington's "very, very strong" sanctions push, as well as "big help" from China, for the potential diplomatic breakthrough.
The officials are the most senior South Koreans to meet Kim since he came to power in 2011 after the death of his father.
Chung Eui-yong assured the public that the main purpose of his trip to the North was to persuade the North to talk with the US.
John Park, the Korea working group director at the Kennedy School of Government at Harvard University, shed further light on the messages Chung was reportedly bringing to Washington.
"We welcome the development of positive trends in the inter-Korean dialogue in light of the visit by the South Korean president's special envoy to Pyongyang, which took place on March 5-6", the diplomat said.
The announcement comes a day after a high-level South Korean delegation returned from Pyongyang where they had cordial meetings with Mr Kim. "For the first time in many years, a serious effort is being made by all parties concerned", Trump tweeted Tuesday.
He urged the Trump administration, however, to continue to take every action possible in applying "maximum pressure" on the North.
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North Korea told the South Korean envoys that it would not need to keep its nuclear weapons if military threats against it are removed and it receives a credible security guarantee, Chung said.
Trump often has derided North Korea's Kim Jong Un as unstable, calling him "rocket man" and taunting him with a tweet describing Trump's nuclear detonation button as "much bigger & more powerful" than Kim's.
"I think we're having very good dialogue", Trump said.
The summit will be held in Peace House on the South Korean side of the border at Panmunjeom.
Seoul is seemingly convinced that the North has affirmed its commitment to the denuclearization of the Korean peninsula.
He had spoken out in the past against his family's dynastic control of North Korea and in a 2012 book was quoted as saying he believed his half-brother lacked leadership qualities.
"There were things discussed in secret [between Chung and Kim in Pyongyang] that are only for US ears", Park said at a Korea Society event in New York. Kim has repeatedly launched intercontinental ballistic missile tests, even claiming to have a "nuclear button" that could launch a nuclear warhead to the United States mainland.
It would be presumptuous to imagine quite yet that the North is chewing over a paradigm shift post the Winter Olympics in February, though visually President Kim appears to have mellowed to an extent.