Mike Pence arrived at the gateway to the Demilitarized Zone dividing the two Koreas on Monday, an AFP correspondent reported, in a show of US resolve hours after North Korea failed in its attempt to test another missile.
The US vice president flew by helicopter into Camp Bonifas, a US-led United Nations command post just a few hundred metres (yards) south of the DMZ. From there, he was expected to move to the truce village of Panmunjom that straddles one of the most heavily militarised borders on Earth.
Tensions between Pyongyang and Washington have soared in recent weeks, as a series of North Korean weapons tests have wrought ever-more bellicose warnings from Donald Trump's administration.
The new and inexperienced US president has indicated he will not allow North Korea to develop an intercontinental ballistic missile capable of delivering a nuclear warhead to the western United States.
A top White House foreign policy advisor on Sunday became the latest Trump official to warn that while diplomatic pressure was preferable, US military action is very much on the table.
"We have a wide array of tools at disposal for the president should he choose to use them," the official said.