United States intelligence agencies believe North Korea has secretly stepped up its uranium enrichment in recent months, while simultaneously seeking concessions from Washington for surrendering its nuclear arsenal, NBC reported Friday.
Bruce Klingner, a former CIA Korea expert now at the conservative Heritage Foundation think tank, said the NBC report showed Mr Trump's statement that North Korea was no longer a nuclear threat was "absurd".
"Mr. Pompeo had to cancel the meeting because of important travel related to North Korea", one official was quoted by the paper as saying.
Trump has been criticized by security analysts for agreeing a joint statement in his summit with Kim that gave no details on how or when North Korea, which has rejected unilateral disarmament, might surrender its nuclear weapons.
The report about North Korean nuclear activity comes a week after U.S. Defense Secretary Jim Mattis suspended the Ulchi Freedom Guardian exercises as well as two other war game operations with South Korean armed forces that were scheduled to take place over the next three months.
North Korea is trying to placate the President and get as many concessions as possible from his administration while at the same holding on to the nuclear stockpiles it considers essential to its longevity as a nation, according to the officials.
"There is absolutely unequivocal evidence that they [North Korea] are trying to deceive the US", an official told NBC.
"There is absolutely unequivocal evidence that they are trying to deceive the United States", he added.
The officials also said the USA had stepped up its intelligence collection against the North, known as the hardest of the hard in terms of espionage targets, and that this gambit was now paying dividends.
"This assessment says there is more than one secret site".
He expressed confidence that North Korea understands the scope of U.S. request for denuclearisation.
The NBC report corroborates recent findings by a watchdog group that published satellite images this week showing work being done on the Yongbyon nuclear research facility.
Vipin Narang, a North Korea expert and professor of worldwide relations at MIT, said Friday that the revelations appeared to be a sign the US intelligence community remains concerned that in declaring victory, the Trump administration was getting far ahead of itself.
The United States has rejected a draft UN Security Council statement presented by China and Russian Federation that calls for easing UN sanctions on North Korea.
The summit in Singapore "wasn't created to solve all issues at once, but to be a starting point to start serious negotiations", Harris said, meant "to establish the modalities for what a complete verifiable irreversible denuclearization means and how we're going to go about that".
Secretary of State Mike Pompeo listens during a Senate Appropriations subcommittee hearing on the FY2019 budget, on June 27, 2018, on Capitol Hill in Washington.