The recent diplomatic developments have given both China and South Korea "every reason to oppose and disregard new sanctions if the USA tries to impose them", said Bilahari Kausikan, the former head of the Foreign Affairs Ministry in Singapore.
"I think it's going to be a very big success", the president said last week. Last year, North Korea tested intercontinental ballistic missiles such as the Hwasong-14 and Hwasong-15.
The choice of Singapore will put the summit on friendly turf for Trump, as the island nation is a strong US ally and the US Navy frequently visits its port.
But he added: "I'm confident that we have a shared understanding of the outcome that the leaders want - certainly President Trump and chairman Kim, but I think president Moon as well".
"My proudest part of this will be when we denuclearize North Korea", the president said.
The press secretary said South Korean officials would not be present at the June summit.
Kim declared his nuclear forced as complete in December, following the country's most powerful nuclear test to date in September and also three flight tests of intercontinental ballistic missiles created to reach the US mainland.
The allure of economic help could be enough for Kim to accept terms to denuclearize, as Pompeo said that there's a chance that North Korea and the USA could become "partners", according to the Los Angeles Times.
"What Kim Jong Un has said publicly and in discussions is that he is prepared to negotiate to achieve complete denuclearization of the Korean Peninsula", he said. "We know who we are dealing with here", said Victoria Coates, of the National Security Council.
Journalists asked Pompeo what such a denuclearization would look like and if it meant carrying out inspections in North Korean nuclear plants.
President Donald Trump speaks as he stands with Tony Kim, second left, Kim Dong Chul, center right, and Kim Hak Song, right, three Americans detained in North Korea for more than a year, after they arrived at Andrews Air Force Base in Md., May 10, 2018.
Amid concerns that North Korea will demand the US withdraw its troops from neighboring South Korea, Kang emphasized that the US military presence there must be "a matter for the US-ROK alliance first and foremost", using an acronym for South Korea's official name, the Republic of Korea.