* Trump, Kim meet for historic summit on Singapore island
* Summit begins with handshakes, smiles, a thumbs up After one on one, top officials join Trump, Kim for talks
* Reuters Live blog - https://www.reuters.com/live/north-korea
By Jack Kim and Steve Holland
SINGAPORE, June 12 (Reuters) - North Korean leader Kim Jong Un and U.S. President Donald Trump shook hands and smiled cautiously as they met at their historic summit in Singapore on Tuesday, in which the two men will look for ways to end a nuclear standoff on the Korean peninsula.
Should they succeed in making a diplomatic breakthrough, it could bring lasting change to the security landscape of Northeast Asia, like the visit of former U.S. President Richard Nixon to China in 1972 led to the transformation of China.
"Nice to meet you Mister President," Kim said as he sat alongside Trump, against a backdrop of North Korean and U.S. flags, beaming broadly as the U.S. president gave him a thumbs up. Trump said he was sure they would have a "terrific relationship".
With cameras of the world's press trained on them, Trump and Kim displayed an initial atmosphere of bonhomie.
"I feel really great," Trump said. "It's gonna be a great discussion and I think tremendous success. I think it's gonna be really successful and I think we will have a terrific relationship, I have no doubt."
Kim replied: "Well, it was not easy to get here. The past has ... placed many obstacles in our way but we overcame all of them and we are here today."
Both men looked serious as they got out of their limousines 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 and holding each other by the arm, before Trump guided Kim to the library where they held a meeting with only their interpreters. Trump had said on Saturday he would know within a minute of meeting Kim whether he would reach a deal.
After some initial exchanges lasting around half-an-hour, Trump and Kim emerged, walking side-by-side through the colonnaded hotel before re-entering the meeting room, where they were joined by their most senior officials.
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. The dollar was at a three-week high and the MSCI index of Asia-Pacific shares was largely unchanged from Monday.
While Trump and Kim search each other's eyes and words for signs of trust or deceit, the rest of the world will be watching, hoping that somehow these two unpredictable leaders can find a way to defuse one of the planet's most dangerous flashpoints.
In the hours before the summit began, Trump expressed optimism about prospects for the first-ever meeting of sitting U.S. and North Korean leaders, while U.S. Secretary of State Mike Pompeo injected a note of caution whether 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," 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!"
The combatants of the 1950-53 Korean War are technically still at war, as the conflict, in which millions of people died, was concluded only with a truce.
On Tuesday morning, Pompeo fed the mounting anticipation of 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.
North Korea, however, has shown little appetite for surrendering nuclear weapons it considers vital to the survival of Kim's dynastic rule.
Sanctions on North Korea would remain in place until that happened, Pompeo said on Monday. "If diplomacy does not move in the right direction ... those measures will increase."
He added: "North Korea has previously confirmed to us its willingness to denuclearise and we are eager to see if those words prove sincere."
The White House said later that discussions with North Korea had moved "more quickly than expected" and Trump would leave Singapore on Tuesday night after the summit, rather than Wednesday, as scheduled earlier.
Kim is due to leave on Tuesday afternoon, a source involved in the planning of his visit has said.
One of the world's most reclusive leaders, Kim visited Singapore's waterfront on Monday, smiling and waving to onlookers, adding to a more affable image that has emerged since his April summit with South Korean leader Moon Jae-in.
The Swiss-educated leader, who is believed to be 34, has not left his isolated country since taking office in 2011, apart from visiting China and the South Korean side of the border Demilitarised Zone, which separates the two Koreas.
Just a few months ago, Kim was an international pariah accused of ordering the killing of his uncle, a half-brother and scores of officials suspected of disloyalty.
The summit was part of a "changed era", North Korea's state-run KCNA news agency said in its first comments on the event.
Talks would focus on "the issue of building a permanent and durable peace-keeping mechanism on the Korean peninsula, the issue of realising the denuclearisation of the Korean peninsula and other issues of mutual concern", it added.
Ahead of the summit, North Korea rejected unilateral nuclear disarmament, and KCNA's reference to denuclearisation of the peninsula has historically meant it wants the United States to remove a "nuclear umbrella" protecting South Korea and Japan.
Trump spoke to both South Korean President Moon Jae-in and Japan's Prime Minister Shinzo Abe on Monday to discuss developments ahead of the summit.
For Kim, the authoritarian leader of a militarised state that has shunned contact with the outside world, the ultimate goal aside from security guarantees would be freedom and support to develop an impoverished economy.
For Trump, achieving a momentous foreign policy success would cement his place in history.
Many experts on North Korea remain sceptical Kim will ever completely abandon nuclear weapons, believing his engagement aims to get the United States to ease crippling sanctions.
"The process could be doomed before it begins," said Kelsey Davenport of the Arms Control Association, adding that a common understanding of denuclearisation was key to success. ($1=1.3336 Singapore dollars)
(Reporting by Christophe Van der Perre; Additional reporting by Soyoung Kim, Dewey Sim, Aradhana Aravindan, Himani Sarkar, Kim Coghill, Robert Birsel, Miral Fahmy, Joyce Lee, Grace Lee, Matt Spetalnick and David Brunnstrom in Singapore and Christine Kim in Seoul; Editing by Simon Cameron-Moore, Raju Gopalakrishnan and Neil Fullick)
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