The official, providing background for reporters Tuesday at the U.S. Army Garrison in Seoul, said no one has found anything "to back up the rhetoric," Stars & Stripes reported.
However, the military still doesn't know if Pyongyang is planning some sort of provocation, whether it would be another nuclear test, launching an intermediate-range ballistic missile or the testing a missile engine.
And, the official said, North Korean leader Kim Jong Un could consider those events as a way to pull back from his escalating threats without starting a war.
"Any one of those things could happen and we could have little to no notice, and we might not know until the missile is airborne," the official said. "I don't think any of us truly know what the true intentions of the Kim regime are."
North Korea maintained its bellicose stance Tuesday, a day after protesters in Seoul burned effigies of Kim Il Sung and his son and successor, late leader Kim Jong Il, Stars & Stripes said. The demonstrations Monday were held on the 101st anniversary of Kim Il Sung's birth.
North Korea said it would refuse to talk with South Korea until Seoul apologized for the "monstrous criminal act."
The North also issued an "ultimatum" to the South, claiming that "retaliatory action will start without any notice."
The United States is "very carefully" monitoring the situation as North Korea was yet to conduct a missile test, the White House said.
White House press secretary Jay Carney said during his daily briefing Monday the North's pattern of behavior reasserted itself in recent weeks.
"And we would not be surprised if that series of provocative actions and bellicose statements were to continue. So we're monitoring the situation very carefully," Carney said. "We are taking the prudent steps that we've talked about in terms of ensuring that our homeland is defended and our allies are defended."
Carney said "any absence of provocative behavior or unhelpful rhetoric is a good thing in this case" but added he would not suggest the United States believes the cycle of the North's behavior has necessarily ended.
Carney said the United States is engaging China, Russia and others and urging them to use their specific influence to prevail on North Korea to "ratchet down" its behavior and rhetoric as they do not help for the cause of stability in the region.
The North's threats stem from tightened U.N. sanctions over its nuclear tests. Recent threats of pre-emptive nuclear strikes against the United States and South Korea have escalated tensions on the Korean Peninsula that have forced North Korea's neighbors to stay on high alert.
U.S. Secretary of State John Kerry Monday ended his Asia trip, which took him to South Korea, China and Japan.
Before returning home, Kerry said in Tokyo the leaders of all three countries he visited were united about North Korea's nuclear missile threat.
"There can be no confusion on this point," he said. "The North's dangerous nuclear missile program threatens not only North Korea's neighbors, but it threatens its own people."
Kerry also said the United States remains "open to authentic and credible negotiations on denuclearization, but the burden is on Pyongyang."