Story highlights

The U.S. will seek a U.N. Security Council resolution imposing sanctions against North Korea in the wake of its nuclear test

The U.S. has also been watching North Korea's efforts to develop its intercontinental ballistic missile program

Washington CNN  — 

The White House expressed skepticism Wednesday over North Korea’s claims of a successful hydrogen bomb test.

Press Secretary Josh Earnest said the initial analysis that had been conducted was “not consistent” with Pyongyang’s assertions.

“There’s nothing that’s occurred in the last 24 hours that has caused the United States government to change our assessment of North Korea’s technical and military capabilities,” Earnest told reporters during the White House daily briefing.

READ MORE: North Korea nuclear test ‘slap in the face’ for China

Earnest rattled off a list of diplomatic steps the administration was taking in response to the nuclear test, saying President Barack Obama was hoping to speak with Japanese Prime Minister Shinzo Abe and President of South Korea Park Geun-gye shortly.

In addition, National Security Advisor Susan Rice met with the Chinese Ambassador to the United States at the White House Wednesday morning, Secretary of State John Kerry had been in touch with his counterparts in the region and Deputy Secretary of State Tony Blinken will travel to the region next week.

“We’ll be working closely with our allies and partners in the region who have their own capabilities (that) can be brought to this collection and analysis of data,” Earnest said, reiterating the United States’ “rock-solid” support of its allies in the region.

“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,” he said.

In addition, the U.S. will seek a U.N. Security Council resolution imposing sanctions against North Korea in the wake of its nuclear test, U.S. officials told CNN Wednesday.

“This is going to have to be fairly substantial resolution,” one of the officials said. “This is very concerning behavior, and we can’t just issue some statement condemning it. It has to be a resolution with teeth.”

The U.S. will also intensify diplomacy with China to support action at the United Nations and urge that it use its influence on Pyongyang, as North Korea’s closest ally and biggest benefactor.

U.S. officials said the fact that China quickly issued a statement condemning the test was encouraging and that they hope it will mean that Beijing will be willing to sign onto a tough resolution.

“The fact the North Koreans did this without giving China warning should be very concerning to Beijing,” one of the officials said. “It means we are dealing with a much more unpredictable leader. We are hoping this will energize the Chinese, not just to be helpful in New York but also with unilateral sanctions and pressure.”

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The U.S. doubted North Korean threats to test a hydrogen bomb last month, the officials said, because they had not demonstrated such capability in the past.

“We didn’t want to overestimate the program or give them too much credit,” another official said. “We still don’t know if they do have that capability. We know it was a test, but we don’t know it was a hydrogen test and it will take some time to determine what it was.”

“If in fact it was a hydrogen explosion, this would be much more serious and indicate a very significant advancement,” the official added. “But we have to wait and see.”

The U.S. has also been watching North Korea’s efforts to develop its intercontinental ballistic missile program, although this official said that “it’s hard to judge the extent of their capabilities. We know they are trying.”