The White House on Wednesday disputed North Korea’s claim that it carried out its first-ever test of a hydrogen bomb, which would be the most powerful weapon in the rogue state’s arsenal.
President Obama’s top spokesman, Josh Earnest, said initial analysis of the nuclear test by the U.S. and international bodies “is not consistent with North Korean claims of a successful hydrogen bomb test.”
Intelligence agencies are continuing to gather evidence to determine the nature of the incident, Earnest said, and a formal determination may not come for weeks.
But analysts said seismic readings of the explosion were smaller than expected from a hydrogen bomb detonation. The magnitude-5.1 tremor felt after the test was the same as the one felt in February 2013, when North Korea set off a less-powerful plutonium weapon.
The swift response underscored growing international concerns about North Korea’s desire to advance its nuclear capabilities, a development that could destabilize the tense Korean peninsula.
“Regardless of how successful the test is ... they have now done four tests and they know a lot about nuclear weapons,” said Jeffrey Lewis, a nonproliferation expert at the Middlebury Institute of International Studies at Monterey. “The bigger takeaway is that they’re going further down this path and that makes it harder to stop.”
Hydrogen bombs, also known as thermonuclear weapons, split atoms apart before slamming them together, in a process called fusion. The two-step process releases vastly larger amounts of energy, resulting in a much more powerful weapon than the ones dropped by the U.S. during World War II.
Pyongyang’s traditional adversaries, South Korea and Japan, joined the United States in denouncing the test. Obama was expected to phone Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-hye Wednesday to further coordinate the global response.
Deputy Secretary of State Tony Blinken is heading to Asia next week, the State Department said — an already scheduled visit that will likely be consumed by the North Korean test.
During a national security meeting in Seoul, Park called the test a “grave provocation” that threatens the “survival and future of our nation.”
“The government — in close cooperation with the international community — should have North Korea pay a price without fail for the latest nuclear test,” she said.
Condemnation from China, North Korea’s closest ally, was significant. Beijing has been able to influence the country’s behavior, and U.S. officials are hoping it could send a message to North Korean leader Kim Jong Un, who has so far resisted international calls to abandon his nation’s nuclear program.
U.S. national security adviser Susan Rice met with China’s ambassador to the U.S., Cui Tiankai, at the White House on Wednesday to discuss the situation, Earnest said.
While it’s nearly impossible to determine the secretive Kim’s motives, the test comes just ahead of his 33rd birthday, on Friday.
This spring, the country is scheduled to hold its first Communist Party congress in almost four decades. Some observers suggested Kim could be trying to consolidate domestic support or extract concessions from China or the West.
“What is true is that North Korea continues to be one of the most isolated nations in the world, and their isolation has only deepened as they have sought to engage in increasingly provocative acts,” Earnest said.
“There is only one path out of the extreme poverty and isolation that they currently face,” he added. “And it’s not a path that is advanced by pursuing nuclear weapons.”
Pyongyang’s assertiveness illustrates Obama’s inability to restrain North Korea throughout his seven years in office, even as he trumpets success with brokering a nuclear deal with Iran.
North Korea has conducted three nuclear tests since 2006, all of which have been condemned by the international community. And diplomatic pressure and sanctions have done little to curb its nuclear ambitions.
“The administration’s North Korea policy is not successful,” said Daryl Kimball, executive director of the Arms Control Association. “They made a limited effort at engagement in 2012, it didn’t work out for them ... and then they go with maligned neglect.”
The test sparked a debate in the 2016 presidential campaign over which candidate is best equipped to respond to boisterous adversaries like North Korea.
Republican critics of Obama were quick to lay blame for the test at the administration’s door.
“Our enemies around the world are taking advantage of Obama’s weakness,” Sen. Marco Rubio (R-Fla.) said in a statement. “If this test is confirmed, it will be just the latest example of the failed Obama-Clinton foreign policy.”
Former Secretary of State Hillary Clinton, the Democratic front-runner, brushed aside that criticism and used the incident to bolster her national security bona fides. She called for stepped-up sanctions on Pyongyang.
“Threats like this are yet another reminder of what’s at stake in this election,” she said in a statement. “We cannot afford reckless, imprudent publicity stunts that risk war. We need a commander-in-chief with the experience and judgment to deal with a dangerous North Korea on day one.”
Julian Hattem and Kristina Wong contributed.
Updated at 8:30 p.m.