Trump said after an Oval Office meeting Friday with North Korea's Kim Yong Chol that he'd be making a mistake not to go forward with the on-again, off-again nuclear summit in Singapore.
MORE: Donald Trump and Kim Jong Un - a timeline of events
Donald Trump and North Korea's Kim Jong Un: A timeline of events
Trump said his meeting with the most senior North Korean to visit the White House in 18 years lasted longer than expected. He said it "went very well."
The president said his June 12 meeting will be "a beginning."
"The process will begin on June 12 in Singapore," he said.