Donald Trump and Kim Jong-un were preparing for their historic summit in Singapore as both sides tried to narrow differences before the two leaders come face to face on Tuesday. It will be the first meeting between a sitting USA president and a DPRK top leader.

Outside the Istana, the presidential palace where Trump was due to meet Singaporean Prime Minister Lee Hsien Loong, well-wishers displayed American flags and a boy held up a sign reading: "I love President Trump!"

The meeting was kicking off at 9 a.m. Tuesday with a handshake between Trump and Kim.

It formally referred to Trump by his full name in the Monday report, including his middle initial - the first time it has done so.

The two leaders discussed bilateral relations as well as the summit and the recent positive developments in the Korean Peninsula. Kim spent the day mostly out of view - until he left his hotel for a late-night tour of Singapore sights, including the Flower Dome at Gardens by the Bay, billed as the world's biggest glass greenhouse.

U.S. and North Korean negotiators met in a Singapore hotel on Monday, seeking to clarify the shape of Tuesday's summit, where Trump has said he intends to guided by instinct.

Alluding to the North's concerns that giving up its nuclear weapons could surrender its primary deterrent to forced regime change, Pompeo told reporters that the US was prepared to take action to provide North Korea with "sufficient certainty" that denuclearization "is not something that ends badly for them".

Even after touching down in Singapore, it was clear that the trade disputes with USA allies in Quebec continued to rankle Trump.

North Korea declared itself a nuclear power in 2005. It heralded the summit as part of a "changed era".

Instead of the Pyongyang-Shanghai- Singapore route that takes six-and-a-half hours but passes over sea routes that are more hard to protect, he flew via Beijing, which took around 10 hours.

It's unclear what Trump and Kim might decide Tuesday. After their initial greeting, the leaders will head into a room for the summit.

Most observers predicted that the outcome would be a short and vague statement build around the ambiguous aim of the "denuclearisation of the Korean peninsula" leaving it to later bilateral meetings to negotiate what that would mean in practice. He told reporters he thinks he will know nearly immediately whether a deal can be made, saying: "I will know, just my touch, my feel".