US Secretary of State Mike Pompeo is due to travel to North Korea to seek agreement on a plan for the country's denuclearisation, despite mounting doubts about Pyongyang's willingness to abandon a weapons program that threatens the US and its allies.
White House spokeswoman Sarah Sanders says the US is "continuing to make progress" in talks with North Korea but declined to confirm or deny media reports of intelligence assessments saying North Korea has been expanding its weapons capabilities.
Pompeo departs the US on Thursday for North Korea and on Saturday will travel from Pyongyang to Tokyo where he will discuss North Korean denuclearisation with Japanese and South Korean leaders, the US State Department said on Monday.
The visit will be Pompeo's first to North Korea since the June 12 summit in Singapore between US President Donald Trump and Kim Jong Un, at which the North Korean leader agreed to "work toward denuclearisation of the Korean Peninsula."
The joint summit statement, however, gave no details on how or when Pyongyang might give up its weapons. US officials have since been trying to flesh out details to produce an agreement that might live up to Trump's enthusiastic portrayal of the outcome.
The US goal remained "the final, fully-verified denuclearisation of (North Korea), as agreed to by Chairman Kim in Singapore," a State Department spokeswoman said.
A US delegation led by US ambassador to the Philippines Sung Kim met with North Korean counterparts at Panmunjom on the border between North and South Korea on Sunday to discuss next steps on the implementation of the summit declaration, the State Department said.
"We had good meetings yesterday and ... the secretary of state will be there later this week to continue those discussions," Sanders told a White House briefing.
Sanders endorsed comments made on Sunday by White House national security adviser John Bolton, who said he believed the bulk of North Korea's weapons programs could be dismantled within a year "if they have the strategic decision already made to do that."
"There is great momentum right now for a positive change and we are moving together for further negotiations," Sanders said.
However, some experts disputed Bolton's optimistic time frame for decommissioning North Korea's weapons, even if North Korea were willing to agree to such moves, amid multiple reports suggesting otherwise.
