"I look forward to seeing Chairman Kim & advancing the cause of peace!" he said.
Experts caution that despite Mr Trump's declaration that North Korea is no longer a nuclear threat, the country has never said it would give up its nuclear weapons programme without similar concessions from the US.
The president predicted North Korea could become an "Economic Powerhouse", one that becomes "a different kind of Rocket - an Economic one!"
Are Trump, Xi and Moon all just keeping up with the Kims? Japan's Fuji TV quoted Vietnamese government sources as saying that Trump administration officials arrived in Da Nang on Wednesday afternoon. "As you know, inter-Korean relations, US-North Korea relations and denuclearization are in a virtuous cycle".
Biegun landed at Osan US Air Base late Friday, foreign ministry spokesman Noh Kyu-duk told AFP.
It said Biegun had agreed with his counterpart Kim Hyok Chol to meet again ahead of the summit. Mr. Biegun is expected to come to South Korea to brief officials as early as Friday. But Washington has insisted that North Korea needs to first take more concrete steps toward denuclearization.
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Biegun said that his discussions with the North were productive and the two sides are committed that they can make 'real progress'.
Attention will be on whether the USA team have offered to lift some economic sanctions in return for Pyongyang taking concrete steps towards denuclearisation.
The Koreas remain technically at war as the Korean War ended with an armistice, not a peace treaty. Abe is called on to deepen cooperation with Washington to ensure that the upcoming Trump-Kim summit leads to improving the security environment for Japan.
At their landmark summit in Singapore past year, the mercurial USA and North Korean leaders produced a vaguely-worded document in which Kim pledged to work towards "the denuclearisation of the Korean peninsula".
The two sides are struggling to narrow their differences about the wording of a final communique the two leaders will announce.
Biegun said last week his Pyongyang talks would be aimed at seeking progress on commitments made in Singapore and mapping out "a set of concrete deliverables" for the second summit.