Observers say they believe North Korea is still years away from having an operational nuclear missile, but they note it does have conventional weapons that pose a threat to countries in the region like South Korea and Japan, both of which are home to thousands of U.S. troops.
Sanctions and drills
The escalation in verbal threats from the North coincided with the tougher U.N. sanctions last month and the annual joint military exercises in South Korea by U.S. and South Korean forces, drills that have aggravated Pyongyang in previous years.
The United States initially responded to the North's invective by publicly drawing attention to its shows of military force in the training exercises, including the flight of nuclear-capable B-2 stealth bombers over South Korea.
But when those moves appeared to further infuriate rather than intimidate Pyongyang, raising worries that they increased the risk of a miscalculation in the crisis, Washington dialed back the displays of strength.
On Saturday, a senior U.S. Department of Defense official said a long-planned missile test in California, scheduled for Tuesday, was being delayed to avoid any misperceptions by North Korea.
And in a sign of the delicate situation in the region, Gen. James Thurman, the top U.S. commander in South Korea, canceled a trip to Washington this week "as a prudent measure," a U.S. military spokesman said Sunday.
Thurman was due to testify before the Senate Armed Services Committee and the House Armed Services Committee.
Analysts have attempted to explain the North's unnerving behavior by suggesting it may be an effort by Kim, who inherited power from his father less than a year and a half ago, to shore up domestic support, particularly with the military.
Another theory is that Pyongyang is trying to secure direct negotiations with Washington, something the United States has long shunned in favor of multilateral talks.
The North Korean regime's recent words and actions appear to be increasingly troubling its key ally, China.
The new Chinese President Xi Jinping, appeared to make an unusual veiled rebuke of North Korea on Sunday.
"Countries, whether big or small, strong or weak, rich or poor, should all contribute their share in maintaining and enhancing peace," Xi said at an international conference, the Chinese state-run news agency Xinhua reported.
No one should be allowed to throw a region into chaos for selfish gains, he said, according to Xinhua.
U.S. Secretary of State John Kerry, who will visit Asia this week, is expected to discuss potential diplomatic incentives for North Korea once it stops its threatening rhetoric, senior administration officials told CNN on condition of anonymity.
"Secretary Kerry agrees that we have to have a robust deterrent because we really don't know what these guys will do," said one senior official, who was not authorized to speak on the issue.
"But he also knows that the North Koreans need a diplomatic off-ramp and that they have to be able to see it."