Yet experts warned Tuesday that the letter could set "unrealistic expectations" for the highly anticipated June 12 summit.
Risch's criteria for success will likely fall short for lawmakers who have seen North Korea offer similarly vague promises in the past, only to back away after securing concessions.
The North, meanwhile, has noted possible stumbling blocks for the talks, including denunciations of upcoming military exercises involving the United States and South Korea.
"This is where you would send someone you could trust", said Hong Min, head of North Korea research at the state-run Korea Institute for National Unification in Seoul. Ri was thought to be a confidant of Kim's father, the late leader Kim Jong Il. However, the possibility of North Korea holding such a trilateral or bilateral summit is being kept open.
"The situation on the Korean Peninsula is facing a rare historic opportunity".
For Kim, recognition of his rule and nuclear power status of North Korea is the prime objective.
North Korean leader Kim Jong Un inspects the construction site of the Wonsan-Kalma coastal tourist area as Kim Su-gil (3rd L), newly appointed director of the General Political Bureau of the Korean People's Army, looks on, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang.
Meanwhile, US allies in the region are privately pressing the administration to maintain pressure on the North over its regional missile program out of concern that Trump could boost the security of the US at the expense of its partners. "This is not blackmail but reality".
"I think [Kim] didn't realize who Donald Trump was at that time, I guess, until he started to read the book and started to get to understand him". Since the Libya model ended up with NATO attacking Libya and Gadhafi killed, North Korea was understandably angry about it.
While removing economic sanctions and enhancing cooperation may not be an issue of conflict between Donald Trump and Kim Jong-un, this will hinge on the progress on the contrasting views on the nuclear question.
The White House on Wednesday morning (AEST) announced that the five-star Capella Hotel would host the historic, June 12 summit between the two leaders as preparations are accelerated for the event.