People watch a TV screen showing file footage of U.S. President Donald Trump, right, and North Korean leader Kim Jong Un during a news program at the Seoul Railway Station in Seoul, South Korea, Saturday, Feb. 9, 2019. AP-Yonhap

U.S. President Donald Trump announced that his second meeting with North Korea's leader Kim Jong-un will take place in Vietnam's capital city and expressed optimism about the communist nation's future.

He made public the summit venue in a Twitter message on Saturday (Seoul time) after Stephen Biegun, the U.S. envoy for North Korea, returned to South Korea following a trip to Pyongyang.

Trump earlier said he will meet Kim in the Southeast Asian nation from Feb. 27-28.

"My representatives have just left North Korea after a very productive meeting and an agreed upon time and date for the second Summit with Kim Jong Un," Trump tweeted. "It will take place in Hanoi, Vietnam, on February 27 & 28. I look forward to seeing Chairman Kim & advancing the cause of peace!"

Trump extolled Kim, who is known to be in his 30s and to have been educated in Europe and whom Trump once nicknamed "Little Rocket Man" for a series of missile launches by his country, especially in 2017.