"I don't believe it would be a successful summit unless you had some kind of commitment on North Korea's part on denuclearization, dismantling, inspections, missiles, nuclear detonations," said Bill Richardson, the former governor of New Mexico and U.S. ambassador to the United Nations, on "This Week" Sunday. "It seems the president is deflating expectations, and that's of concern."
Richardson added that "this summit may be a dud" without concrete progress on denuclearization.
The president will depart Washington on Monday for the Hanoi summit, to participate in the face-to-face meeting with Kim. Their first summit was held in Singapore in June 2018.
After the Singapore summit, Trump and Kim signed an agreement on a range of issues, including denuclearization. However, members of Trump's intelligence community and many leading North Korean experts note that North Korea has taken no concrete steps toward denuclearization since then.
Jung Pak, the chair of Korea studies at the Brookings Institution and a former CIA analyst, told George Stephanopoulos on "This Week" that the messaging surrounding the second summit has moved away from denuclearization and that the change is "problematic."
"I think there has been a profound shift in talking about peace and normalization with North Korea rather than the nuclear issues," Pak said. "And I think that's really problematic, because the whole point of a summit between the two leaders ... is to get dismantlement and North Korea to completely abandon its nuclear weapons."
U.S. intelligence has suggested that while North Korea has publicly destroyed some testing sites, there is still activity in the country that would be inconsistent with denuclearization.
Dan Coats, the director of national intelligence, said in congressional testimony last month that it is unlikely that North Korea would ever completely give up a nuclear weapons program because "its leaders ultimately view nuclear weapons as critical to regime survival."
The president, however, has repeatedly touted the fact that North Korea hasn't conducted any major tests of nuclear weapons or missiles since the summit. He also said earlier this month that he is "in no rush for speed."
Some of the president's supporters are also reinforcing the call for real, solid commitments from North Korea in this second summit.
Tom Bossert, the president's former homeland security and counterterrorism adviser and current ABC News contributor, said that there has been "backpedaling and dishonesty from the last summit."
He added that the second summit "will be a dud if [Trump] comes out and tries to varnish this as a success without any real actionable activity."
Pak said Trump is "making a mistake of mirror imaging" when he views Kim as similar to himself.
"He's speaking in terms of as if Kim is another businessman," she said. "But Kim is a dictator and a highly authoritarian -- of a highly authoritarian regime -- and who needs his nuclear weapons for legitimacy and his own survival."
Richardson added that "we have got to continue talking. ... The relationship of the two leaders, that's good. However, the president should listen to his advisers, and his advisers have been -- I think -- very specific."
Trump and Kim meet in Vietnam on Thursday.