Robert King, who served as U.S. envoy on North Korean human-rights issues under the Obama administration, said Trump has used human rights as an instrument to get Kim Jong Un to negotiate on nuclear weapons, but not as a policy priority in its own right.
However, Trump and his aides insist that a USA -led "maximum pressure" campaign of the toughest-ever economic sanctions, diplomatic action and military threats is what has drawn Kim to the negotiating table. That group will then expand a third time over a working lunch before the delegations depart.
Mr Trump said he felt "really great" about the meeting.
"It's gonna be a great discussion and I think tremendous success", Trump said.
Kim responded with a smile.
"There were obstacles but we overcame them to be here".
It is also unclear whether US officials will raise human rights issues in meetings with the North Koreans.
AFP 2018 Saul Loeb World Follows Every Step of Historic Trump Kim Summit
Actually, says another group, there will indeed be disarmament, a peace treaty ending the Korean War and North Korea's emergence as a contributing member of the worldwide community - but just not right now.
Following that test, North Korea declared its state nuclear program was complete.
Trump and Kim will start their historic summit with a one-on-one session with translators.
But he has since lowered expectations, saying the talks would be more about starting a relationship with Kim for a negotiating process that would take more than one summit.
"The fact that I am having a meeting is a major loss for the US, say the haters & losers", Trump tweeted about three hours before the summit.
What is unclear whether the summit will lead to any type of substantive outline of an agreement in which North Korea will halt its program and agree to denuclearize, and what kind of verification procedure it would accept. "If diplomacy doesn't move in the right direction, sanctions will increase".
Both Trump and Kim arrived on Sunday to Singapore, chosen as the site of the summit for its reputation as a safe and orderly place and the fact that is has diplomatic relations with both North Korea and the US.
Its report added: "He said Singapore is clean and handsome and every building is stylish as he heard of in the past, adding he is going to learn a lot from the good knowledge and experience of Singapore in various fields in the future".
"Thanks PM Lee for spending $20 million of taxpayers money, which can. help a lot of needy families in Singapore to survive", posted one Facebook user.