US President Donald Trump arrived on Sunday in the Demilitarised Zone dividing the Korean peninsula ahead of a meeting with the North's leader Kim Jong Un.
The expected encounter, only suggested a day earlier by Trump on Twitter, comes with negotiations over the North's nuclear programme in stalemate since the leaders' last summit in Vietnam in February.
Accompanied by South Korean President Moon Jae-in, an earnest-looking Trump toured an observation post overlooking North Korean territory, with a US military officer pointing out the sights.
Trump is expected to hold a brief encounter with Kim in the DMZ, which would be their third face-to-face meeting after a historic initial summit in Singapore and a second in Hanoi that collapsed without an agreement.
The two would "just shake hands quickly and say hello because we haven't seen each other since Vietnam", Trump said earlier.