While Trump was optimistic about prospects for the summit between the old foes, USA secretary of state Mike Pompeo injected a note of caution ahead of the first-ever meeting of sitting U.S. and North Korean leaders, saying it remained to be seen whether Kim was honest about his willingness to denuclearise.
"We've had multiple deals with North Korea", said Green, who served as director of Asian affairs for the National Security Council under President George W. Bush.
Among the three dozen or so North Koreans seen at breakfast on Monday were some of the regime's most powerful men, usually only spotted by North Korea watchers in photographs published in state media as they line up at official events.
Shortly after a group of suited North Korean diplomats set out from their Singapore hotel on Monday for talks with US officials on the eve of a historic summit, a bigger group of North Koreans headed out in summery shirts for some shopping.
North Korean leader Kim Jong Un met Singaporean Prime Minister Lee Hsien Loong at his office in Singapore Sunday evening in his first diplomatic outing of his visit to the country ahead of Tuesday's landmark summit with U.S. President Donald Trump.
"As the venue and time of the summit have already been announced, security for Kim Jong Un will be tighter than for any other VIPs", said the professor, who was the first academic to establish a university major in South Korea on guarding and protection. The two will later be joined by officials and have lunch together. She acted as his envoy to the Winter Olympics in the South, spent nearly the whole of his first summit with the South's Moon Jae-in at his side, and accompanied him to China to meet President Xi Jinping.
"I do not know of a single USA official - and we talked to a lot of them - or Japanese official below the level of the president who thinks North Korea is going to denuclearize", Green said.
As Trump was trying to build a bridge with Kim, he was smashing longtime alliances with Western allies, withdrawing from the G7 joint communique, escalating a trade fight and launching blistering criticism against Canadian Prime Minister Justin Trudeau following the summit in Quebec on the weekend. The move was in reaction to North Korea's criticism of USA vice president Mike Pence's statement that the country could meet the same fate as Libya if it failed to meet a nuclear deal with the US.
Not all US officials have joined Messrs.
"If diplomacy doesn't move in the right direction, sanctions will increase", Secretary of State Mike Pompeo says.
A woman walks past a cannon barrel stuffed with flowers in a symbolic gesture of peace at Fort Siloso in Singapore, as preparations continue for Tuesday's Trump-Kim summit.
In exchange for North Korea's cooperation, the administration is offering Kim both security guarantees and economic aid. Trump and Kim planned to meet one on one, joined only by translators, for up to two hours before admitting their respective advisers, a US official said.
Trump, who has complained about the cost of those troops, might welcome the opportunity, though a troop withdrawal would also reinforce doubts about America's commitment to the Asia-Pacific region. "From what I can tell from (Trump's recent comments at the White House), they're not going to be asked to do much".
The president has allowed that persuading Kim to abandon North Korea's nuclear weapons program will require more than a single sit-down. -North Korea summit in Singapore.
Trump suggested last week the two leaders may sign a peace agreement to formally end the Korean War 65 years after the armistice that ceased military hostilities.