The leaders of North and South Korea signed a declaration on Friday agreeing to work for the "complete denuclearization of the Korean peninsula."

At their first summit in more than a decade, the two sides announced they would seek an agreement to establish "permanent" and "solid" peace on the peninsula.

"The joint goal is to agree to have a Korean Peninsula without any nuclear arsenal," South Korean President Moon Jae-in said in a joint news conference in Panmunjom, the border truce village

North and South Korea say they will jointly push for talks with the United States and also potentially China to officially end the 1950-53 Korean War, which stopped in an armistice and left the Koreas still technically at war.

The declaration included promises to pursue military arms reduction, cease "hostile acts," turn their fortified border into a "peace zone," and seek multilateral talks with other countries, such as 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 declaration said.

There was no mention of specific steps toward disarmament. North Korea has previously said it is contingent upon the removal of American troops, nearly 30,000 in number, stationed in South Korea.

The statement came just hours after Kim Jong-un became the first of North Korea's leaders, which included his father and grandfather, to cross into South Korea.

"When we met each other, we realized — we cannot be separated," said Kim. "We are one nation and that's how I felt. We are living next door to each other, there's no reason we should fight each other."

The two countries have agreed to hold high-level military talks in May to reduce tensions, with South Korea's president scheduled to visit the North sometime in the autumn. The leaders were also said to pledge to maintain contact through a newly established hotline between the countries.

Propaganda broadcasts that the countries have been blaring at each other across their heavily armed border will cease next week, they said, with the broadcasting equipment to be dismantled.

The sides also agreed to:

Hold family reunions in August of those separated by the war.

Set up a permanent communications office.

Work toward connecting some roads and railways.

There has been widespread skepticism about whether Kim is ready to abandon the nuclear arsenal his country has defended and developed for decades, with a flurry of missile tests conducted within the last two years.

'I don't think he's playing': Trump

"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," Kim said after the agreement was signed.

Friday's historic summit between North Korea's Kim Jong-un, second from left, and South Korea President Moon Jae-in concluded with a banquet at Panmunjom. Kim's wife Ri Sol-ju, left, shares a toast with Moon's Kim Jung-sook, right. (Korea Summit Press Pool/AFP/Getty Images)

Kim is scheduled to meet with Donald Trump in late May or June, the first time the current leaders of the two countries will have done so.

The U.S. president, while at a photo opportunity with reporters Friday at the White House alongside German Chancellor Angela Merkel, didn't want to doubt Kim's sincerity.

"I don't think he's playing," said Trump. "It's never gone this far. I don't think it's ever had this enthusiasm for them wanting to make a deal."

The North Korean dictator recently met with Mike Pompeo, now confirmed as U.S. secretary of state, in a meeting that was not publicly revealed until several days after it had occurred.

"The relationships are building and building strongly," said Trump.

Trump said two or three sites are being considered as a location for his meeting with Kim and that the U.S. wouldn't be "played like a fiddle" in negotiations, as he claims previous administrations have in talks when Kim's father and grandfather led the secretive Asian nation.

South Koreans wave unification flags to wish for a successful inter-Korean summit at the Imjingak Pavilion in Paju, South Korea on Friday. (Lee Jin-man/Associated Press)

Christopher Hill, a former U.S. ambassador to the Republic of Korea and a former negotiator with North Korea, told CBC News there's still a long way to go to realize the goals outlined.

"But nonetheless, I don't see how anyone can ignore the significance of what happened."

Kim's new year's speech, in which he touted his country's strength but also announced he would consider sending a team to the Olympics, signalled a willingness to talk with his neighbours to the south, Hill said.

There's been a thaw in recent months — including at the Winter Olympics in South Korea, where the rival nations marched under a common flag and fielded a joint women's ice hockey team.

He said he thinks it's clear that Kim Jong-un is different from his father, Kim Jong-il, who ruled from 1994 until his death in 2011.

"Whether he's better, or whether he's more devious, we have to wait and see."

Moon steps into North

The summit Friday began with the leaders smiling and exchanging greetings near the blue buildings that straddle the border at Panmunjom. The village is one of the few places where there are no barbed wire fences or minefields between the two countries.

"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 as he grasped Moon's hand across the border.

Security personnel accompany a vehicle transporting North Korean leader Kim Jong-un after the morning session. (Korea Summit Press Pool/Reuters)

"It was your big decision to make it here," said Moon in return, who obliged when invited to step over into what is considered North Korean territory.

After talks in the morning, the two men went back to their separate sides for lunch, Kim driven in a black limousine and escorted by a dozen bodyguards in dark suits and ties jogging alongside the vehicle.

In the afternoon, they planted a memorial tree and watered it with water from rivers in the South and North. As the afternoon sun set, the two men sat at a small table on a blue footbridge along the border for a half-hour private chat, at turns laughing and looking serious.

Sanctions must remain: NATO

In the evening, a dinner banquet was held, attended by the wives of Kim and Moon — respectively, Ri Sol-ju and Kim Jung-sook. The menu was said to feature items such as bibimbap, cold noodles and Korean-style Swiss rosti potato, and it was also attended by cultural figures from both countries.

Kim left in a black Mercedes Benz limousine for the trip north of the border at about 9:30 p.m. local time.

In China, which has been a patron of North Korea, Foreign Ministry spokeswoman Hua Chunying told reporters at a briefing Friday that Beijing wishes that the meeting between Kim and Moon will achieve a "positive result."

Japan, which saw some of the North's missile tests fall into the Sea of Japan, welcomed the outcome of the summit.

South Korean President Moon Jae-in talks with North Korean leader Kim Jong-un during their meeting at the Peace House in Panmunjom inside the demilitarized zone separating the two Koreas on Friday. (Korea Summit Press Pool/Pool via Reuters)

Prime Minister Shinzo Abe praised the talks Friday as a "forward-looking move."

Boris Johnson, British secretary of state for foreign affairs, and NATO's secretary general Jens Stoltenberg both hailed the meeting but were quick to point out that international sanctions against North Korea must remain in place until it curbs its nuclear ambitions.