President Donald Trump has published a letter sent to him by North Korean supreme leader Kim Jong Un, in which the young ruler praises his US counterpart but does not mention any commitments to abandon nuclear weapons.
The South Korean president, Moon Jae-in, also downplayed the North Koreans' antics, stating it was all part of Pyongyang's "strategy" toward extracting more concessions from the United States.
The source said that Kim did not see any need to hold dialogue with Japan before his summit with South Korean President Moon Jae-in in April, instead favoring relations with the United States, China and Russian Federation.
While the summit represented a major thaw in relations, US sanctions on North Korea, among the most stringent in the world, will remain in place until the Kim regime implements "final, fully verified denuclearization", US State Secretary Mike Pompeo said last week.
On Monday Trump reiterated his confidence in Kim.
Pompeo traveled to the North last week to try to iron out the details amid criticism that the USA administration had already given up too much, too soon and was being played.
North Korean representatives didn't show up for scheduled talks with the US about returning the remains of fallen American soldiers.
The remains of some USA soldiers were last returned in 2007, when then-New Mexico Governor Bill Richardson visited Pyongyang.
Despite that, Trump hailed the July 6 letter as a "very nice note", saying "Great progress being made".
Pompeo was in Pyongyang from Friday to Saturday to try to flesh out a bare bones denuclearisation deal made during last month's historic summit between Kim and US President Donald Trump.
That number includes 7,702 who are missing in action, with an estimated 5,300 believed to have been lost in the North, according to the Hawaii-based DPAA, which oversees the effort.
President Trump met with North Korean Dictator 26 days ago.
Mr Pompeo had said progress was made during his two-day visit to Pyongyang. Despite the secretary's attempt to put a positive spin on the visit, as soon as he was out of the country, North Korea criticized his "unilateral and gangster-like" demands and called the talks "regrettable".
"The U.S. side had had discussions with the North with an aim to hold the talks as early as July 12, but it appeared that the North was not ready for the talks", the source told Yonhap News Agency on condition of anonymity.
"We have to see the USA defense ministry's response, but the UNC reportedly gave a positive signal to North Korea, so there is a good chance of the talks taking place on Sunday", the source said. "I have it for him", Trump said.