It has been nearly three weeks since President Donald Trump surprised the world with his "on-the-spot" acceptance to meet with North Korean leader Kim Jong Un by the end of May, and the White House is scrambling to nail down the details.
Aside from a proposed agenda to discuss the North's nuclear program, the White House has yet to produce a date, time, location or a list of Trump administration participants.
Adding to the disarray, Kim has been suspiciously silent, at least in public — and it has cast a shadow of doubt over the potential meeting. What's more, Kim traveled on a secret train trip to Beijing, which concluded Wednesday, but even that was shrouded in mystery.
Some experts view Kim's visit, the first known journey abroad since he assumed power in 2011, as preparation for upcoming summits with the U.S. and South Korea.
However, the North's history of breaking promises is all too familiar to the last American diplomat to successfully secure a deal with North Korea — only to see it fall apart a few years later.
"The South Korean National Security Advisor is saying that Kim Jong Un is prepared to meet with President Trump AND give up his nuclear weapons if the meeting goes well," former U.S. Ambassador Robert Gallucci, who is now chairman of the U.S.-Korea Institute and a Georgetown professor, wrote in an email to CNBC. "One would think that the North would have a comment."
Why Kim has been quiet
Other experts suspect that Kim was taken aback by Trump's acceptance.
"The South Koreans have been pushing the North Koreans to interact with the Americans, so it may be the case that Kim made the gesture of an invitation to demonstrate his good faith to the South Koreans, not expecting that it would go anywhere," Joshua Pollack, senior research associate at the Middlebury Institute of International Studies at Monterey, California, told CNBC. "So I suspect that Kim also may have been surprised."
Lisa Collins, a fellow with the Korea Chair at the Center for Strategic and International Studies, said the North Korean dictator could be weighing his options.
"North Korea may have been surprised by Trump's immediate acceptance of the offer to hold a U.S.-DPRK summit and may be carefully planning a response," Collins told CNBC. "Or they could also be dragging out their answer to create even greater suspense and drive more attention to the issue. The intense focus on the summit outcome could then be used as bargaining leverage for negotiations."
History and mystery
The summit, currently slated to occur by the end of May, would mark the first time a sitting U.S. president meets vis-a-vis with a leader from the reclusive regime.
Speaking to reporters on Tuesday, White House press secretary Sarah Huckabee Sanders said the administration was working on the meeting but hinted that it may not transpire by May.
"The offer was extended and accepted and we are continuing to move forward in that process. We still don't have a set time or date on that front," Sanders said.
The invitation to meet, delivered in person by a South Korean envoy on March 8, is the most significant development in years of intermittent negotiations about North Korea's nuclear weapons program.
South Korea's National Security Office head Chung Eui-yon said Kim "expressed eagerness to meet President Trump as soon as possible."
The third-generation North Korean leader also promised to "refrain from any further nuclear or missile tests" while talks are underway, Chung said. "President Trump appreciated the briefing, and said he would meet him to achieve permanent denuclearization."
Meanwhile, the U.S. continues to wait for nations like South Korea or China to shed light on the North's next move.
WATCH: Understanding Kim Jong Un's rumored China visit
