WASHINGTON (Reuters) - Leaders of the United States and North Korea will meet for the first time when President Donald Trump and Kim Jong Un hold a summit on June 12 in Singapore where the U.S. side will try to persuade Pyongyang to give up its nuclear weapons.

The two men - whose countries are still technically at war - exchanged fiery rhetoric last year over North Korea's attempts to build a nuclear weapon that could reach the United States.

But tensions have since eased greatly, starting around the time of the North's participation in the Winter Olympics in South Korea in February.

"The highly anticipated meeting between Kim Jong Un and myself will take place in Singapore on June 12th. We will both try to make it a very special moment for World Peace!" Trump wrote on Twitter.

His announcement came just hours after three Americans who had been held prisoner in North Korea arrived at a U.S. military base outside Washington, having been released by Kim as a gesture ahead of the summit.

Trump said on their arrival that he believed Kim, who has led North Korea for seven years and is believed to be in his

mid-30s, wanted to bring North Korea "into the real world."

"I think we have a very good chance of doing something very meaningful," Trump said. "My proudest achievement will be - this is part of it - when we denuclearize that entire peninsula."

New U.S. Secretary of State Mike Pompeo has visited Pyongyang twice in recent weeks - once as head of the CIA - but there has been no sign that he cleared up the central question of whether North Korea will be willing to bargain away nuclear weapons that its rulers have long seen as crucial to their survival.

"PHOTO OP" WORRY

In a speech on the floor of the U.S. Senate, Democratic Leader Chuck Schumer warned Trump against going too far too fast in Singapore. The Republican president, Schumer said, should insist upon strong, verifiable commitments from North Korea on disarmament.

"I worry that this president, in his eagerness to strike a deal and get the acclaim and a photo op, will strike a quick one and a bad one, not a strong one, not a lasting one," Schumer said.

During Trump's presidency, Kim has overseen weapons tests that rattled the United States, South Korea and Japan as the North Korean leader attempted to showcase his military's progress on medium- and long-range missiles and atomic weapons.

Trump has credited a U.S. "maximum pressure" campaign for drawing North Korea to the negotiating table and vowed to keep economic sanctions in place until Pyongyang takes concrete steps to denuclearize.

But former spy chief Kim Yong Chul, director of North Korea's United Front Department, said in a toast to Pompeo over lunch in Pyongyang this week: "We have perfected our nuclear capability. It is our policy to concentrate all efforts into economic progress...This is not the result of sanctions that have been imposed from outside."

Kim recently promised to suspend missile tests and shut a nuclear bomb test site.

North Korea is still technically at war with the United States and its ally South Korea because the 1950-53 Korean War ended in a truce, not a treaty.

Smiling and holding hands, Kim and South Korean President Moon Jae-in held a rare round of talks at the heavily fortified demilitarized zone between the countries at the end of April, pledging to pursue peace after decades of conflict.

South Korea said on Thursday it had high hopes for the summit.

“We welcome the North Korea-U.S. summit to be held in Singapore on June 12. We hope the denuclearization of the Korean peninsula as well as permanent peace on the peninsula will successfully come about through this summit.”

The choice of Singapore will put the summit on friendly turf for Trump, as the island nation is a strong U.S. ally and the U.S. Navy frequently visits its port.

U.S. officials had looked at several sites other than Singapore for the historic meeting but each was seen as problematic.

Trump’s own preference was for the demilitarized zone between the two Koreas, but aides argued that this would look too much like Trump going to Kim’s turf.

A quick trip to Pyongyang was also seen as bad optics for Trump, U.S. officials said. Mongolia was considered but was seen as too close to China, they said.

(Reporting by Doina Chiacu and Steve Holland; Writing by Richard Cowan; Editing by Chizu Nomiyama and Alistair Bell)

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