Photo: Donald Trump and Kim Jong-un prepare to head away for talks. (AP)

President Donald Trump and North Korea's Kim Jong-un open nuclear summit in Singapore

12 Jun 2018,

US President Donald Trump and North Korean leader Kim Jong-un posed for a handshake, smiling cautiously, as they began historic talks on the nuclear standoff on the Korean Peninsula.

"Nice to meet you Mr President," Mr Kim said as he sat alongside Mr Trump, against a backdrop of North Korean and US flags, beaming more broadly as the US President gave him a thumbs-up.

With the cameras of the world's press trained on them, Mr Trump and Mr Kim built an initial atmosphere of friendship.

"I feel really great. We're going to have a great discussion and will be tremendously successful," Mr Trump said.

"It's my honour and we will have a terrific relationship, I have no doubt."

Mr Kim replied: "It was not easy to get here … there were obstacles but we overcame them to be here."

Both men looked serious as they got out of their limousines at about 11:00am (AEST) for the summit at the Capella Hotel on Singapore's Sentosa, a resort island with luxury hotels, a casino, manmade beaches and a Universal Studios theme park.

But they were soon smiling for photos and exchanging pleasantries before heading away for what were expected to be one-on-one talks, with translators only.

They emerged about half an hour later before moving onto a meeting involving top diplomats from both sides.

Mr Trump had said on Saturday he would know within a minute of meeting Mr Kim whether he would reach a deal.

The summit is the first between a North Korean leader and a sitting US president.

As the two leaders met, Singapore navy vessels, and air force Apache helicopters patrolled, while fighter jets and an Gulfstream 550 Airborne Early Warning aircraft circled.

Financial markets were largely steady in Asia and did not show any noticeable reaction to the start of the summit.

In the hours before the summit began, Mr Trump expressed optimism about the prospects for the meeting, while US Secretary of State Mike Pompeo injected a note of caution on whether Mr Kim would prove to be sincere about his willingness to denuclearise.

Officials of the two sides held last-minute talks to lay the groundwork for the summit of the old foes, an event almost unthinkable just months ago, when they were exchanging insults and threats that raised fears of war.

Staff-level meetings between the United States and North Korea were going "well and quickly", Mr Trump said in a message on Twitter on Tuesday.

But he added: "In the end, that doesn't matter. We will all know soon whether or not a real deal, unlike those of the past, can happen!"

On Tuesday morning, Mr Pompeo fed the mounting anticipation of a diplomatic breakthrough, saying: "We're ready for today."

He earlier said the event should set the framework for "the hard work that will follow", insisting that North Korea had to move toward complete, verifiable and irreversible denuclearisation.