U.S. President Donald Trump and North Korean leader Kim Jong Un both arrived in Vietnam February 26 for a second summit.
The two leaders will meet in Hanoi on February 27-28 to discuss North Korea's nuclear-weapons and missile programs.
There has been speculation that the two leaders would discuss agreeing to a formal end to the Korean War, which was frozen by an armistice agreement in 1953.
Trump flew into Vietnam's capital, Hanoi, on Air Force One.
Kim arrived by train early in the day after a three-day, 3,000-kilometer journey from North Korea's capital, Pyongyang, through China. He completed the last leg of his journey from a border station to Hanoi by car.
Prior to leaving Washington, Trump posted on Twitter: "With complete Denuclearization, North Korea will rapidly become an Economic Powerhouse. Without it, just more of the same. Chairman Kim will make a wise decision!"
Speaking to a gathering of governors in the White House earlier on February 25, Trump predicted "a very tremendous summit."
Secretary of State Mike Pompeo said on Fox television on February 24 that he hoped for "a substantive step forward" at the summit.
"It may not happen, but I hope that it will," Pompeo said.
Vietnamese authorities have promised tight security for the event and no information has been released concerning the venue for the summit.