SEOUL/WASHINGTON (Reuters) - The leaders of North and South Korea pledged at a historic summit on Friday to work for “complete denuclearization” of the Korean peninsula, but U.S. President Donald Trump said he would maintain pressure on Pyongyang through sanctions ahead of his own unprecedented meeting with North Korea’s Kim Jong Un.

The meeting between Kim and South Korean President Moon Jae-in produced a day of dramatic images and a sweeping declaration of goodwill. But it was short on specific commitments and failed to clear up the question of whether Pyongyang is really willing to give up nuclear missiles that now threaten the United States.

Meeting at the heavily fortified Demilitarized Zone that has divided the Koreas for more than six decades, Kim and Moon announced they would work with the United States and China this year to declare an official end to the 1950s Korean War, and establish a permanent peace agreement.

In an event marked by smiles, handshakes and embraces, they also promised to pursue phased arms reduction, cease hostile acts, transform their fortified border into a peace zone and seek talks involving other countries, including the United States.”The two leaders declare before our people of 80 million and the entire world there will be no more war on the Korean peninsula and a new age of peace has begun,” the two sides said.

But even as they agreed on a common goal of a “nuclear-free” peninsula, they stopped short of spelling out exactly what that meant or how it might come about.

Speaking at a news conference in Washington with German Chancellor Angela Merkel, Trump, who has raised expectations that his own planned meeting with Kim in coming weeks will deliver tangible results, expressed hope it would be productive.

(Korea: a land divided - tmsnrt.rs/2KdXMcS)

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‘NOT REPEAT MISTAKES’

But he added: “We will not repeat the mistakes of past administrations. Maximum pressure will continue until denuclearization occurs.”

Trump has said Kim must completely abandon his nuclear missile program and has credited his campaign of sanctions and military threats with bringing Kim to the negotiating table.

Earlier he told reporters would not allow himself to be “played like a fiddle” by North Korea like past U.S. administrations.

Many analysts say that while sanctions may be hurting North Korea, Kim may believe he has the upper hand and is unlikely to give up his full nuclear capability, considering it vital to the survival of his family dynasty.

In past negotiations, North Korea has demanded the United States withdraw its troops and remove its “nuclear umbrella” of support for the South.

The United States stations 28,500 troops in South Korea.

On Friday, U.S. Defense Secretary Jim Mattis said the United States would seek to build trust with North Korea through confidence building measures, but deferred to diplomats questions about the future U.S. military presence under any peace treaty.

Kim, widely regarded by many Americans and South Koreans as a brutal dictator, appeared to use the summit to soften his international image.

He became the first North Korean leader since the Korean War to set foot in South Korea after shaking hands with Moon over a concrete curb marking the border.

Scenes of Moon and Kim joking and walking together were a striking contrast to last year’s barrage of North Korean missile tests and its largest ever nuclear test, which raised fears of war.

U.S. intelligence officials said it had been an impressive charm offensive by Kim, but their view of him and their belief in his desire to keep his nuclear weapons had not changed.

A U.S. administration official, who did not want to be identified, said Trump’s aides were being briefed by South Korean officials and were looking for clarity on whether Kim made any meaningful commitment to nuclear disarmament.

In a statement, U.S. Vice President Mike Pence said any North Korea promises would be “met with reservation, vigilance, and verification.”

U.S. Secretary of State Mike Pompeo, who over the Easter weekend became the first U.S. official ever known to have met Kim, told a news conference after a NATO meeting in Brussels he believed Kim was serious about try reaching a deal.

“The economic pressure that has been put in place by this global effort that President Trump has led has led him to believe that it’s in his best interest to come to the table and talk about denuclearization.”

The Kim-Moon meeting was meant in part to lay some of the groundwork for a Trump-Kim summit, which would be the first encounter between sitting leaders of the two countries.

Slideshow ( 25 images )

Trump, who has exchanged nuclear threats and personal insults with Kim in the past year, said only time would tell, but he did not think Kim was “playing.”

“It’s never gone this far. This enthusiasm for them wanting to make a deal ... We are going to hopefully make a deal.”

Trump said two countries were under consideration as the site for his meeting with Kim, which he has said could be in late May or early June.

China, North Korea’s main ally, welcomed Kim and Moon’s statement and said it was willing to keep promoting political solutions. China is wary of being sidelined by a thaw between the two Koreas and by the Trump-Kim summit.

Russia said it was ready to facilitate cooperation between North and South Korea, including in railway transport and energy. Japanese Prime Minister Shinzo Abe welcomed the summit and said he expected North Korea to take concrete steps to carry out its promises.

As part of efforts to reduce tensions, North and South Korea agreed to open a liaison office, stop propaganda broadcasts and allow divided families to meet.

Slideshow ( 25 images )

Days before the summit, Kim said North Korea would suspend nuclear and long-range missile tests and dismantle its only known nuclear test site.

But deep scepticism remains about Kim’s intentions, and Daniel Russel, until recently the most senior U.S. diplomat for Asia, said that the joint declaration fell short of an explicit commitment to denuclearization.

Jonathan Schanzer, an expert at Washington’s Foundation for Defense of Democracies think tank, said North Korea had made promises many times in the past. “The question now is whether Kim Jong Un is ready to deliver, or if this is a prelude to yet another deliberate effort to spurn the West,” he said.

Former U.S. assistant secretary of defense for East Asia, Abraham Denmark, said that despite the warm images and friendly words, “there is still no trust and no clear way ahead.”

“We must remember: North Korea is still North Korea. Kim is still the same person he was when he purged potential rivals, imprisoned thousands of his people, and had his relatives killed. This was a hopeful moment, but extreme caution is well warranted.”

It is not the first time leaders of North and South Korea have declared hopes for peace. Two earlier summits, in Pyongyang in 2000 and 2007, failed to halt North Korea’s weapons programs or improve relations in a lasting way.

Kim alluded to past failures after the latest agreement was signed, saying: “We will make efforts to create good results by communicating closely, in order to make sure our agreement signed today before the entire world, will not end as just a beginning like previous agreements before today.”

Moon agreed to visit Pyongyang this year, the leaders said.

FIRST ACROSS THE LINE

Moon greeted Kim at the military demarcation line where the men smiled and shook hands. In an unplanned moment of theater, Kim invited Moon to step briefly across into North Korea, before the two leaders crossed back into South Korea holding hands.

“I was excited to meet at this historic place and it is really moving that you came all the way to the demarcation line to greet me in person,” Kim said.

“A new history starts now. An age of peace, from the starting point of history,” Kim wrote in Korean in a guest book in the South’s Peace House before talks began.

In a private session, Kim told Moon he came to the summit to end the history of conflict and joked he was sorry for waking Moon up with his early morning missile tests, a senior South Korean presidential official said.

Moon and Kim continued their talks into a dinner banquet and later, with their wives, watched a music performance and held hands as they watched a montage of photos from their summit set to a K-pop song that included the words “be a family again.”