How much Kerry's backroom diplomacy with China was a factor in North Korea's calmer behavior has yet to be determined. Some U.S. officials acknowledge China is singing a helpful tune, but have yet to see serious moves by Beijing that would indicate they are putting serious pressure on the regime.
"We believe the views the Chinese have expressed publicly about North Korea are also being expressed privately," one senior U.S. official said. "Whether they are having an effect on North Korea, we don't know. I don't think we can say it's promising or not at this stage."
Other factors are also at play. Spring is typically the time of year North Korea's military returns to the fields for planting. With North Korea's economy in tatters, the military does double duty as farmers, laborers and manufacturers.
And there is the unfortunate realization that North Korea's time out, however welcome, is just that -- a time out. Although Pyongyang is undoubtedly pleased the U.S.-South Korea military exercises are over, officials and experts are worried North Korea will feel more emboldened once again.
"This can go on for months with North Korea where nothing is happening or tomorrow they could launch a missile," one senior U.S. official said.