"We'll know pretty soon if they're going to operate in good faith or not", the anonymous official said, as recounted by Reuters.
For the first time in years, North Korea will skip its annual "anti-U.S. imperialism" rally, according to the Associated Press.
North Korean officials did not have any on-the-record comments on the move, but AP staff said they confirmed on Monday the event had been called off.
Trump and Kim spent each spent three days in Singapore for the June 12 summit where the two pledged to work on ending North Korea's nuclear programme and improve ties.
The official went on to say the USA will soon know whether or not Kim Jong Un plans to stick with the agreement.
Sampaoli downplays talk of unrest, vows to get best of Messi
It's part of a disappointing worldwide run in which Messi's only medal with Argentina came 10 years ago at the Summer Olympics. Lionel Messi and Argentina hit the training ground on Saturday with renewed hope of qualifying for the World Cup last 16.
Last Thursday, state TV showed Kim on his third visit to China, disembarking from his aircraft with his wife Ri Sol-ju affectionately holding on to his arm. That's going to be worked on.
U.S. Secretary of State Mike Pompeo has said he will not put a timeline on negotiations for North Korea's denuclearization, contradicting a senior defense official who said Washington would soon present a timeline to North Korea with "specific asks".
"Any statements by DoD personnel regarding the DPRK are exclusively in reference to the military aspects of the negotiations", White added, mentioning the "indefinite suspension of major exercises or logistical support for the dignified transfer of remains". But Lee noted the diplomatic rapprochement on the peninsula, with two inter-Korean summits preceding the meeting in Singapore - after which Trump announced the suspension of joint military exercises with the South, the US's security ally.
"One thing is really clear, is that the Kim Jong Un leadership is very much anxious about making important changes, exposing the system to the influence of outside powers", said Yonsei University's Bong Young-shik.
The day after the Singapore summit Pompeo said Washington hoped to achieve "major disarmament" by North Korea within Trump's current term, which ends on 20 January 2021. "I heard it myself when I visited there as Central Intelligence Agency director, I heard it myself when I visited Pyongyang as Secretary of State and I heard it again where there was a group together with the President and Chairman Kim". North Korea has also tried to withhold its participation in family reunions until certain political conditions are met, such as halting activists in the South from sending outside information into the North.