An advance team, led by deputy chief of staff Joe Hagin, has held meetings with the North Korean team in Singapore this week. The envoy spent the last two days in New York City in talks with Secretary of State Mike Pompeo in an effort to put the Singapore summit back on track.
Itsunori Onodera said North Korea agreed to give up nuclear weapons as early as 1994, but has continued to develop them in secret and until previous year threatened surrounding countries with a series of ballistic missile launches.
Trump cautioned on Thursday that while he hopes a planned summit in Singapore on June 12 between the US and North Korea is still in the cards, he wants it to be a "meaningful" meeting.
Eight minutes later, according to the Washington Post, Trump admitted that he hadn't even opened the letter when a reporter asked if he sent anything back.
Last week, Trump had abruptly canceled the historic Singapore meeting arranged by US and North Korean officials after North Korea sent a bellicose letter critical of Vice President Mike Pence.
Former U.S. officials who have negotiated with North Korea have cautioned that the Kim family regime has violated past deals aimed at curbing the nation's nuclear and ballistic missile programs.
During a press appearance, Trump said it was a "very nice" and "very interesting" letter.
The envoy, Gen Kim Yong-chol, hand-delivered a letter from the North Korean leader to President Trump. I never said that it will happen in one meeting. Trump said that Xi "has helped me quite a bit with this".
He was speaking at an worldwide security conference in Singapore, which is hosting the June 12 summit. "We're going to start a process".
Mr. Kelly then escorted the North Korean delegation along the Rose Garden colonnade to the Oval Office, where they met with Mr. Trump, Mr. Pompeo and others.
With relations thawing, the United States has pledged to help rebuild North Korea's economy if it agrees to give up its nuclear weapons.