The US envoy was also likely to have discussed with his counterpart protocol and security matters for the upcoming Trump-Kim summit.
North Korea's economy is considered to be sluggish due largely to the worldwide sanctions, aimed at preventing it from developing ballistic missiles and nuclear weapons.
Trump is now confirming that the talks will be on February 27 and 28 in Hanoi, and said he expects North Korea to "become a great Economic Powerhouse" because of how great and capable Kim is.
Casting doubt on North Korea's willingness to dismantle its nuclear arsenal and possibly throwing a wrench into talks in Vietnam is a confidential report from the United Nations which claims the communist state is still developing its nuclear and ballistic missiles.
Earlier this week, Trump announced that he would be meeting Kim in Vietnam, but he did not disclose the city.
National Assembly Speaker Moon Hee-sang and the leaders of ruling and opposition parties embarked on a weeklong trip to the USA on Sunday morning.
Trump left the first summit by declaring that "everybody can now feel much safer than the day I took office".
A US government spokesman has indicated that Vietnam was chosen as the venue for the second US-North Korea summit to symbolize the thriving partnership between former enemies.
Yet critics have said the deal signed between by Trump and Kim in June included no specific language on a plan or timeline for disarmament, making it hard to enforce.
The anniversary is a holiday in North Korea.
The two envoys will meet again before the summit.
Both sides said they were committed to denuclearisation, but with no details of how this would be carried out or verified. The margin of error was 3.1 percentage points.
The two world leaders previously met in Singapore in June 2018.
Experts say the most likely scenario in Vietnam is that the concerned parties - North and South Korea, the USA, and China - to declare a formal end to the war as a political statement.
A fresh example came in December, when a phone call with Turkish leader Recep Tayyip Erdogan prompted Trump's declaration that he's withdrawing USA soldiers stationed in Syria.
The Blue House spokesman said he heard that Pyongyang and Washington had agreed to continue negotiations at a third country in Asia in the week beginning February 17.
Can the US Speed up North Korean Denuclearization?
Meanwhile, South Korea expects the U.S.to exempt South-North economic cooperation from sanctions. Then, Kim pledged to work toward the "complete denuclearization" of the Korean Peninsula, without providing a clear timetable or roadmap.
Experts have more recently warned that North Korea's compliance in talks is no more than smoke and mirrors. Trump will be hoping that China-Vietnam relations may open the eyes of Kim who if adequately supported may well do a Vietnam on China. "They can't let another summit be called a failure".
On Wednesday, Stephen Biegun, U.S. special representative for North Korea, arrived in Pyongyang for talks about the envisioned summit.
There has been speculation the meeting would be in Da Nang.
While in the U.S. view North Korea has yet to take concrete steps to give up its nuclear weapons, it complains that Washington has done little to reciprocate for its freezing of nuclear and missile testing and dismantling of some facilities.
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The distance: It is not too far from North Korea, so it is easier for Kim to reach by plane.
This story was reported by The Associated Press.