Negotiations between the United States and North Korea to pave the way for the summit between their two leaders on June 12 have kicked into higher gear since last Saturday's impromptu meeting between South Korea's President Moon Jae In and North Korean leader Kim Jong Un.
Meetings between American and North Korean officials are under way simultaneously in the truce village of Panmunjom, on the North and South Korean border, and in Singapore.
The goal at Panmunjom is to develop a framework agreement on denuclearisation. The American delegation there is led by Mr Sung Kim, a veteran of previous nuclear negotiations with North Korea and currently the US ambassador to the Philippines.
Mr Joseph Hagin, a deputy White House chief of staff, is leading a separate delegation to Singapore, to make decisions on the arrangements for the potentially historic but off-again, on-again summit between the North Korean leader and President Donald Trump.
At Panmunjom, Mr Sung Kim's team reportedly includes Ms Allison Hooker, a low-key but respected Korea specialist on the National Security Council. Ms Hooker has been to North Korea before, and accompanied Mr Trump's daughter and top aide Ivanka Trump to the closing ceremony of the Winter Olympics at Pyeongchang in South Korea in February.
Mr Randall Schriver, Assistant Secretary of Defence for Asian and Pacific Security Affairs, is also part of the team.
The North Korean team in Panmunjom is led by Ms Choe Son Hui, a vice-foreign minister whom Mr Sung Kim has dealt with many times before - most notably when she was deputy director of the North Korean Foreign Ministry's North American Affairs Bureau and was involved in the 2003 to 2009 six-party talks to denuclearise North Korea. That round of talks ended with Pyongyang walking out.
The two teams met yesterday on the northern side of Panmunjom. More meetings are reported to be scheduled for today.
"Our United States team has arrived in North Korea to make arrangements for the summit between Kim Jong Un and myself," Mr Trump tweeted on Sunday. "I truly believe North Korea has brilliant potential and will be a great economic and financial nation one day. Kim Jong Un agrees with me on this. It will happen!"
The core issue between the two sides remains finding common ground on denuclearisation.
According to reports based on sources, Washington wants Pyongyang to ship its nuclear warheads, or possibly its intercontinental ballistic missiles, to the US - most likely to a facility in Oak Ridge, Tennessee. Some analysts expect there may be agreement on a symbolic shipment of some components of the North Korean nuclear programme.
But Pyongyang's version of denuclearisation differs from that of the US; for one thing, it will demand concessions in return for gradual denuclearisation.
The key may be what the US proposes.
Analysts say that the North will most importantly need iron-clad security guarantees if it is to genuinely give up its nuclear weapons. Such an arrangement would need to be preceded by a formal end to the Korean War - which was only halted with an armistice in 1953.
The Korea Herald yesterday quoted a top South Korean official as saying that this would be the crux in any deal. "Ultimately, denuclearisation and guaranteeing the North Korean regime can be considered the axis of the agenda (for the US-North Korea summit)," the official was quoted as saying.
News of the meetings in Panmunjom and Singapore came as officials in Seoul started discussing the possibility of Mr Moon joining the summit between Mr Trump and Mr Kim. Analysts said Mr Moon - who seems to have built trust with Mr Kim through two summits in a month - can help to bridge the gap between the US and North Korea and mediate if necessary.