"Otto Warmbier is a very special person, his parents are good friends of mine", Trump told reporters from Singapore after he and North Korean leader Kim Jong Un signed an agreement committing to "complete denuclearization".
"It's important for us to remember that it's largely words at this point, and that we have to look for actions, particularly from North Korea", Panetta said during an interview with FOX Business' Neil Cavuto on Tuesday.
President Moon Jae-in on Monday acknowledged that solving the North Korean nuclear problem could take a couple of years.
In 2003, Libyan leader Muammar Gaddafi allowed independent inspectors to verify that its nuclear and chemical programs were shut down.
Secretary of State Mike Pompeo tweeted that the U.S. negotiating team "delivers for America's swagger".
Trump and Vice President Mike Pence attempted to clarify Bolton's comments in May, but Pyongyang was back on the offensive: North Korea's state-run media outlet referred to Pence as "ignorant and stupid" for making "unbridled and impudent remarks".
The Wyoming, Ohio, native was in North Korea with a tour group when he was detained for allegedly stealing a propaganda poster from a hotel.
North Korea blamed botulism and ingestion of a sleeping pill and dismissed torture claims.
North Korea also serves as a valuable buffer state between China and USA forces in South Korea. North Korea historically has called for the removal of the USA "nuclear umbrella" over South Korea and Japan.
In follow-up talks on the establishment of new relations, the US and North Korea will likely hold discussions on ending hostilities.
I think, suspending military exercises is the one thing the U.S. can rather un-problematically do in order to get concessions from North Korea, because lifting sanctions, at this point, before North Korea moves forward toward denuclearization, will encounter a lot of resistance from other people in the American political system.
"We're not there yet", he said.
"It was brutal", the President said.
However, Trump and Kim may need one more meeting to discuss existing problems, according to the U.S. president.
"This new commitment to denuclearize is actually more vague and even weaker than the 2005 six-party joint statement and the 1992 inter-Korean Joint Denuclearization Declaration", said Duyeon Kim, a research fellow at the Korean Peninsula Future Forum, describing two major diplomatic statements.
Trump and Kim signed a document on Tuesday stating that Pyongyang would work toward "complete denuclearization of the Korean Peninsula".