U.S. envoy meets North Korean officials at DMZ

North Korean leader Kim Jong-un smiles during a visit to the Chemical Material Institute of the Academy of Defence Science in Hamhung

Noting that the U.S. is very well aware of North Korea's pattern of behaviour over decades of negotiating with the U.S., he said that the Trump administration knows exactly what the risks are of them using negotiations to drag out the length of time they have to continue their nuclear, chemical, biological weapon programmes and ballistic missiles.

In announcing Pompeo's travel plans on Monday, White House spokeswoman Sarah Sanders said the United States was "continuing to make progress" in talks with North Korea.

White House national security adviser John Bolton said on Sunday he believed the bulk of North Korea's weapons programs could be dismantled within a year, although some experts say the complete process could take far longer.

Bolton said the "going to try and proceed to implement what the two leaders agreed to in Singapore", specifically "how to dismantle all of their WMD and ballistic missile programs in a year".

But the continued talks come as reports from U.S. intelligence agencies reveal that Pyongyang is continuing to work on its nuclear and intercontinental ballistic missile systems while engaging in negotiations. "We're not going to provide a timeline for that".

South Korea's Hyundai company built a basketball stadium in Pyongyang during the "Sunshine Period" of engagement between the North and South and a joint game was played there in 2003.

U.S. officials "met with North Korean counterparts in Panmunjom to discuss next steps on the implementation" of the declaration, a U.S. Embassy official said.

However, Jackson said, Kim's involvement with what he saw as a disappointing summit in Singapore showed the limits of this approach.

North Korea invited reporters from several countries - including the United States, South Korea, China, Russia and Britain - to record the event. "And without those inspections, we can have no guarantee that North Korea is not cheating again".

Secretary of State Mike Pompeo will head to Pyongyang today to reach an agreement with Kim Jong-un over the country's denuclearisation plan.

An analysis of recent satellite photos also indicated that North Korea is completing a major expansion of a factory in the northeast that produces key parts of nuclear-capable missiles, two researchers at the Middlebury Institute of International Studies at Monterey, California, said in a joint post Monday. Team Prosperity defeated Team Peace 103-102, with North Korea's Ro Suk Yong scoring 18 points, according to pool reports.

"I don't want to comment on that specific report", Bolton said.

Noerper added that North Korea has made a commitment to denuclearize before the whole global community. He also said he trusted Kim to follow through on denuclearization.

Mr Trump said the U.S. "would be at war with North Korea" if he had not stepped in and skilfully halted Kim Jong-un's nuclear ambitions - despite USA intelligence leaks suggesting North Korea is still expanding its nuclear arsenal.

Cho, the South Korean unification minister, said he felt "deeply moved" upon arrival because he could sense the change in relations in the past few months.

Some experts have said a one-year program would be hard, with Stanford University's Siegfried Hecker, a leading expert on the North's nuclear program, proposing a 10-year roadmap instead.