"South Korea will have mixed feelings toward Trump's remarks", said Lee Il-woo, a director at Korea Defense Network in Seoul.
Rep. Ed Royce of California, who is chairman of the House Foreign Affairs Committee, applauded Trump for pursuing peace through diplomacy, but he also said Kim had "gained much" Tuesday, "including an apparent promise" from Trump to suspend military drills.
Trump and Kim signed a document on Tuesday stating that Pyongyang would work toward "complete denuclearization of the Korean Peninsula".
"The greatest achievement of the summit was that Trump's comments show his confidence in resolving any issues [with Kim]", Nam said in a brief meeting with a small group of reporters in Singapore.
Only hours before the summit, Mattis told Pentagon reporters that, as far as he knew, the issue of USA troops in South Korea would not be part of any discussion in Singapore.
"His country has to be denuked, and he understood that, he fully understood it", Trump said.
Trump reiterated plans to end joint military exercises between the United States and South Korea. Cory Gardner told reporters that they were assured joint military exercises would continue.
"We just hope President Trump knows what he was getting into".
"There were no surprises", she said.
The presidential office said the measures were particularly needed at a time "when a variety of serious dialogues have been held between the North and the US for the denuclearization of the Korean peninsula and the establishment of relations".
In the past, Trump has repeatedly referred to Kim as "little rocket man" and promised to bring "fire and fury" to the country if it endangers the United States.
But Panetta, who previously worked for President Barack Obama, said there are a "huge number of issues" that will actually involve the denuclearization of North Korea, which owns an estimated 20 to 60 nuclear weapons with about 141 sites that can produce them. "That's not what you have to do", Trump said. "History is a record of people who take action and rise to a challenge".
"The Korean government should keep vigilant", Qassemi warned ahead of the historic meeting in Singapore between Mr. Trump and North Korean dictator Kim Jong-un.