On the eve of their historic and unprecedented summit, President Donald Trump and North Korean leader Kim Jong Un prepared Tuesday for a meeting that could define the fate of millions, along with their own political futures, with Trump forecasting a "nice" outcome and Kim spending the day out of view.

Both sides were finalizing preparations for the meeting, which was to kick off at 9:00 am Tuesday with a handshake between Trump and Kim, an image sure to be devoured around the world. 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. The official was not authorized to speak publicly about internal deliberations and insisted on anonymity.

The summit will be the first between a North Korean leader and a sitting American president. In Singapore, the island city-state hosting the summit, the sense of anticipation was palpable, with people lining spotless streets Monday waving cell phones as Trump headed to meet Singapore's Prime Minister Lee Hsien Loong.

As Trump and Lee sat down for a working lunch at the Istana house, Trump sounded optimistic, telling Lee, "we've got a very interesting meeting in particular tomorrow, and I think things can work out very nicely." Trump had earlier tweeted about the "excitement in the air!"

Meanwhile, US and North Korean officials huddled at the Ritz-Carlton hotel Monday ahead of the sit-down aimed at resolving a standoff over Pyongyang's nuclear arsenal. A second round of meetings was planned for the afternoon as officials worked to lay the groundwork for progress to be made Tuesday, according to the official familiar with the preparations. Delegates were outlining specific goals for what Trump and Kim should try to accomplish and multiple scenarios for how key issues can be resolved.

The meetings also served as an ice breaker of sorts as the teams worked to get better acquainted after decades of minimal US -North Korea contact. In a sign of lingering tensions, the North Koreans have been closely scrutinizing all American staffers are slated to be in any US-North Korea meetings, including translators, photographers and logistical staff, asking how they can be sure the American are not actually spies.

Trump and Kim arrived in Singapore on Sunday, both staying at luxurious and heavily guarded hotels less than half a mile apart, with Trump at the Shangri-La Hotel and Kim at the St. Regis Hotel.

"The entire world is watching the historic summit between (North Korea) and the United States of America," Kim told Lee through an interpreter when they met Sunday.

US Secretary of State Mike Pompeo, the former CIA director, spent the morning preparing with his top advisers, aides said. He was joined in Singapore by Ambassador Sung Kim, the US envoy to the Philippines; and Ambassador Michael McKinley, a career diplomat Pompeo recently tapped to be his senior adviser.

Pompeo in a statement described the meetings as "substantive and detailed" and said Trump was "well-prepared" to meet the North Korean leader.

Pompeo traveled twice to Pyongyang in recent months to lay the groundwork for Trump's meeting, becoming the most senior member of Trump's team to spend time with Kim face to face.

Trump has said he hopes to make a legacy-defining deal for the North to give up its nuclear weapons, though he has recently sought to minimize expectations, saying additional meetings may be necessary.

Asked Saturday about his goals, he said: "Well, I think the minimum would be relationship. You would start at least a dialogue, because, you know, as a deal person, I have done very well with deals."

The North has faced crippling diplomatic and economic sanctions as it has advanced development of its nuclear and ballistic missile programs.

Experts believe the North is close to being able to target the entire US mainland with its nuclear-armed missiles, and while there's deep skepticism that Kim will quickly give up those hard-won nukes, there's also some hope that diplomacy can replace the animosity between the US and the North.

As Trump was trying to build a bridge with Kim, he was smashing longtime alliances with Western allies, withdrawing from the G-7 joint communique, escalating a trade fight and launching blistering criticism against Canadian Prime Minister Justin Trudeau.

Trump continued to tweet angrily at Trudeau from Singapore, saying Monday "Fair Trade is now to be called Fool Trade if it is not Reciprocal."

One top Trump adviser cast the move as a show of strength before the Kim meeting. Economic adviser Larry Kudlow told CBS News in Washington that "Kim must not see American weakness," adding that by criticizing new tariffs, Trudeau was "pouring collateral damage on this whole Korean trip."

While advisers insist Trump has been reviewing briefing materials, he insists his gut instincts will matter most when he gets in the room with Kim. He told reporters he thinks he will know almost immediately whether a deal can be made, saying: "I will know, just my touch, my feel. That's what I do."

Pyongyang has said it is willing to deal away its entire nuclear arsenal if the United States provides it with reliable security assurances and other benefits. But there are major doubts, given how hard it has been for Kim to build his program and that the weapons are seen as the major guarantee to his holding onto unchecked power.

Any nuclear deal will hinge on the North's willingness to allow unfettered outside inspections of the country's warheads and nuclear fuel, much of which is likely kept in a vast complex of underground facilities. Past nuclear deals have crumbled over North Korea's reluctance to open its doors to outsiders.

Another possibility from the summit is a deal to end the Korean War, which North Korea has long demanded, presumably, in part, to get US troops off the Korean Peninsula and eventually pave the way for a North Korean-led unified Korea.

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. China and South Korea would have to sign off on any legal treaty.