Meetings between American and North Korean officials are under way 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 United States delegation there is led by Mr Sung Kim, the US ambassador to the Philippines and a veteran of nuclear negotiations with North Korea.
Mr Joseph Hagin, a deputy White House chief of staff, is leading a separate delegation to Singapore, to make decisions on arrangements for the summit between North Korean leader Kim Jong Un and US President Donald Trump.
Denuclearisation remains the core issue. The North will need ironclad security guarantees if it is to give up its nuclear weapons. This would need to be preceded by a formal end to the Korean War, which was halted with an armistice in 1953.