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(CNN) — US President Donald Trump shook the hand of North Korean leader Kim Jong Un when the two met Tuesday morning local time, an extraordinary display of diplomacy that reflects an unprecedented gamble for two unpredictable leaders intent on making their mark on history.

Singapore was crackling with anticipation for the historic moment when Trump met Kim, the first time ever for a US president and a North Korean leader.

Trump is putting his extraordinary gamble with North Korea to the test, sitting for unprecedented talks with the rogue kingdom’s despotic leader in what he hopes will amount to a historic breakthrough.

Whether nuclear disarmament is indeed the outcome of Tuesday’s summit won’t be known for years, if not decades. But the dramatic act of extending his hand to one of America’s longtime adversaries will forever illustrate Trump’s gut-driven, norm-shattering tenure.

Trump departed his hotel at just past 8 a.m. and arrived at the summit location — a white-shuttered hotel on the tourist island Sentosa — about 10 minutes later. Kim arrived shortly afterward.

The men were preparing in separate rooms before their 9 a.m. handshake. They greeted each other atop a red carpet in front of a row of US and North Korean flags — a previously unthinkable sight.

Tweeting from his hotel room in the pre-dawn hours on Tuesday, Trump sought to heighten the suspense.

“Meetings between staffs and representatives are going well and quickly….but 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!” he wrote.

After the men shook hands, they repaired inside for one-on-one talks. In that first meeting they’ll be joined only by translators, a break from standard practice of having at least one aide present for high-stakes huddles.

Later in the day, advisers will enter the room for a larger bilateral session and a working lunch. The White House said Trump would be joined by Secretary of State Mike Pompeo, chief of staff John Kelly, national security adviser John Bolton and the US Ambassador to the Philippines Sung Kim, who has lent his Korea expertise to the talks.

In the lead-up to the summit, US and North Korean officials were convening contentious final-hour negotiations in a Ritz Carlton hotel here in a bid to narrow gaps on key aspects of the meeting. In question is Pyongyang’s precise commitment to nuclear disarmament, and the security guarantees the US is willing to offer in return.

One US official said the two sides were working to craft a joint US-North Korea “statement of understanding” that could be released after the talks. The language in that document has been the fraught topic of discussion at the 11th-hour negotiations.

It’s not clear what the US side has been able to extract from the North Koreans in terms of their willingness to get rid of their nuclear weapons or allow inspectors into the country to catalogue the scale of their program.

That hasn’t stopped Trump from heightening anticipation for the summit, which he views as a landmark event that his predecessors could never have accomplished.

“I just think it’s going to work out very nicely,” he said during a lunch with Singapore’s prime minister on Monday.

Trump has taken keen interest in the pageantry of the day, insisting the pictures beamed around the world reflect a commanding leader making a decisive, world-altering move. At the same time, he’d admitted he doesn’t believe he requires extensive preparation to take stock of Kim.

Instead, he told reporters last weekend he would rely on “my touch, my feel” to assess the young and mercurial leader. He added he would know within minutes whether Kim was serious about negotiating away his nuclear weapons and has threatened to politely walk out if Kim doesn’t meet his expectations.

At one point, Trump suggested to reporters the talks could extend to a second or even a third day if they were going well. He was originally scheduled to leave on Wednesday. But on Monday evening, the White House announced Trump would depart for Washington by 8 p.m. Tuesday evening in Singapore, leaving little time for follow-up. Before he leaves he’ll sit for an interview with his friend, the Fox host Sean Hannity, and convene a media availability for other reporters.

A US official confirmed to CNN Trump’s departure was moved up by more than 12 hours because Kim set his own departure for shortly after the summit, as first reported by Bloomberg. The official cautioned, however, that the schedule could always change if meeting goes well and there is more to discuss. The meeting is intended to be “start of a relationship,” the official said, and there could be more to come between both sides if things go well.

In the same statement, the White House said the talks between US and North Korean officials were moving “more quickly than expected,” though didn’t elaborate on what precisely that meant for Trump’s stated goal of securing North Korea’s complete and verifiable denuclearization.

Tuesday’s meeting, convened at a luxury hotel on the island of Sentosa, comes just three months after Trump accepted North Korea’s invitation for talks on the spot. It was an extraordinarily compressed timeline for the landmark summit, one that left aides scrambling to initiate communication with the hermit nation.

The sides first spoke through intelligence channels, with US analysts working to determine Kim’s true willingness to abandon a nuclear program started by his grandfather and viewed by Pyongyang as a security blanket from outside aggressors.

Pompeo, who led the outreach as CIA director, traveled twice to North Korea for preliminary talks. His sessions with Kim amounted to the most robust contact ever between the United States and the North Korean leader, providing critical information about a man about whom little is known.

Talks proceeded at multiple levels, including logistical discussions to allay Kim’s fears of being deposed while traveling further afield than he ever has before as the country’s leader. The site of the historic talks was a matter of intense speculation before the US President announced on Twitter it would occur here in Singapore, the flashy Southeast Asian city-state that has eagerly accommodated the spectacle.

More than 2,500 journalists have convened here, with each leader’s every movement tracked carefully. Trump mostly remained inside his Shangri-la hotel on the day before the summit, emerging only to meet with his Singaporean counterpart at the presidential palace. Later in the day, he met with senior advisers and phoned the leaders of Japan and South Korea.

Kim, meanwhile, was spotted taking a moonlit stroll around the high-end Marina Bay Sands hotel and casino, which is owned by GOP mega-donor Sheldon Adelson. Kim was cheered by onlookers who caught sight of the dictator, who until earlier this spring was not believed to have ever left North Korea as supreme leader.