WASHINGTON -- The latest round of threats exchanged by North Korea and the United States is dragging on longer and taking on a more virulent tone than in the past, provoking deep concerns among American officials and their allies.
Following blustery warnings by Kim Jong Un, North Korea's 30-year-old leader, and videos depicting North Korean attacks on the United States, the Obama administration took the unprecedented step last week of sending two stealth bombers to South Korea as part of an ongoing military training exercise.
But despite the escalating tensions, U.S. officials said they have focused more closely on what North Korea is doing than on what it is saying.
"Putting on a show is not the same as taking action. Describing the situation as akin to war is not to be remotely confused with wanting a war, let alone going to war," said a senior administration official, who spoke on condition of anonymity to discuss the volatile situation.
The senior administration official said that U.S. military commanders are closely watching the situation, which has escalated since North Korea conducted a nuclear weapons test in December. In addition, officials cited new levels of cooperation and mutual confidence between the United States and allies in South Korea and Japan.
While a direct attack on U.S. forces on the mainland or in the Pacific Ocean seems unlikely, non-government analysts said the rising tensions increase the risk of some form of limited armed conflict. North Korea recently cut off its military phone line with the South, which is used to coordinate logistics along the demilitarized border buffer.
On Saturday, North Korea reiterated that it considered the Korean Peninsula back in "a state of war" and it threatened to shut down a factory complex it jointly operates with South Korea that stands as the last significant symbol of cooperation.
The industrial park, the 8-year-old Kaesong complex in the North Korean border town of the same name, is a crucial source of badly needed cash for the heavily sanctioned North. It funnels more than $92 million a year in wages for 53,400 North Koreans employed there, and its operation has survived despite years of military tensions.
Also Saturday, the White House said it is taking seriously new threats by North Korea but also noted Pyongyang's history of "bellicose rhetoric."
Some experts noted that South Korea has also adopted a more aggressive rhetorical posture. Senior officials quoted anonymously in the media have suggested that plans have been drawn up for "surgical strikes" in North Korea.
"The level and scope of the rhetoric is stronger than in the past," said Scott Snyder, a Korea expert at the Council on Foreign Relations. "This time, we've seen a higher level of threat, delivered at a higher level."
"There's room for miscalculation right now," he said.
Earlier this month, the Pentagon announced it was significantly bolstering America's missile defense capabilities on the West Coast. Defense Secretary Chuck Hagel said Thursday the United States has no option but to take Pyongyang's threats seriously.
But the decision to include B-2 bombers flown from Missouri in the military exercise with South Korea was made some time ago, the senior official said, adding that U.S. "strategic air assets" would be a part of the annual exercise "from this point forward."
Christopher Hill, a former U.S. diplomat who served as ambassador in Seoul in 2004 and later led a negotiating team that sought to eliminate the North Korean nuclear threat, said the current standoff appears "more serious" than past ones. It also comes as the North appears to be attempting to bolster Mr. Kim's military credentials.
Mr. Kim has been an enigma since he took the helm of the country in December 2011 after his father's death. The country's leaders have taken great pains in recent months to bill the world's youngest head of state as a capable commander in chief, granting him additional titles and medals.
"The explanation could be that this is linked to trying to give this third-generation camp a little more of a profile," Mr. Hill said. "I don't think he has really connected with the North Korean people. They could be looking to show he's a tough guy."
The New York Times and Associated Press contributed.