Now North Korean officials will nearly certainly emphasise preventing any sudden mishaps in Kim Jong Un's first visit to a foreign country other than China or South Korea since taking power, said Kim Doo-hyun, professor of protection politics at Korea National Sport University.
For Richard Armitage, a former senior diplomat in the George W. Bush administration, Tokyo runs a very real risk of finding itself out in the cold after the Trump-Kim talks.
They include the Capella Hotel on Sentosa Island, the summit venue, and the places surrounding the Shangri-La Hotel and the St. Regis Hotel where Trump and Kim are expected to stay, respectively.
At the hotel lobby, grim-faced North Korean security guards warned other hotel guests not to take pictures as Kim walked to his Mercedes Benz limousine.
This will be the first summit of its kind between a leader of North Korea and a sitting USA president.
Yet even as he turned his attention to the summit, Trump continued his blistering attacks on Canadian Prime Minister Justin Trudeau, tweeting "Fair Trade is now to be called Fool Trade if it is not Reciprocal".
The Singaporean authorities have designated the sites related to the summit as the special event areas from Sunday through Thursday. He has not left his country since taking office in 2011 other than to visit China and the South Korean side of the Demilitarised Zone on the border.
The official media had reported that the two leaders plan to meet, but offered few specifics, including where and when.
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Before leaving Tokyo, Abe clearly outlined what would need to happen for the summit to be a success: tangible progress on curbing the North's nuclear and ballistic missile programs, as well as answers about the Japanese nationals kidnapped by Pyongyang in the 1970s and 1980s. White House press secretary Sarah Huckabee Sanders said Sung Kim, the United States ambassador to the Philippines who has taken the lead on policy negotiations with the North, will hold a "working group" with a North Korean delegation.
During the meeting, Mr Lee and Mr Kim discussed Singapore-North Korea relations, as well as developments in the North and the region.
Trump's efforts to make peace with a country that is still technically at war with the United States received backing from his fellow G7 members in a joint statement issued after the U.S. president's departure.
April 18: Mr Trump confirms that Mike Pompeo, then the Central Intelligence Agency chief, had met Mr Kim secretly in North Korea and said "a good relationship was formed" heading into the anticipated summit. "From that time onwards we started selling 30-40 units a day", he told Reuters in an interview at the project's showroom, decorated with water-spouting statues of Singapore's unofficial mascot, the mythical Merlion.
Some critics have said the summit is being rushed through, with Trump keen to chalk up his first major foreign policy achievement.
It's unclear what Trump and Kim might decide Tuesday.
"My suspicion remains that he is going to try to get as much sanctions relief as possible without having to give up his weapons", said Sen. Trump has also raised the possibility of further summits and an agreement ending the Korean War by replacing the armistice signed in 1953 with a peace treaty. The impersonator, who would give only his stage name Howard X, said he was held by immigration authorities for two hours before being released and told to steer clear of summit venues.
White House press secretary Sarah Huckabee Sanders said Trump spent his flight from Canada to Singapore "meeting with his staff, reading materials and preparing for his meetings in Singapore".
Both North Korea and the United States have expressed expectations for the outcomes of their first summit meeting set to open in Singapore on Tuesday.