The White House has expressed doubt over claims by Pyongyang in regard to successful testing of a hydrogen bomb, citing inconsistency between the data obtained and North Korea’s allegations.
"The initial analysis that has been conducted ... is not consistent with North Korea's claim of a successful hydrogen bomb test," White House spokesman Josh Earnest said on Wednesday.
He noted that the test, which Pyongyang announced on state TV earlier in the day, has not changed Washington’s evaluation of North Korea’s capabilities.
"There is nothing that has 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 said.
US President Barack Obama is set to talk with Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-Hye, who have expressed concerns over the matter, he added.
United Nations Security Council has condemned the move, which would mean North Korea has obtained a far more powerful weapon than it previously had.
China has joined other world powers, including Britain and France, to censure the move.
Before Pyongyang’s announcement, a fake earthquake was detected in the country, whose seismic wave was viewed as smaller than detonation of a true thermonuclear weapon.
The North Koreans were said to have increased the yield of normal device using tritium.
South Korea experts said the seismological data from the test are likely to have arisen from a simple atomic device based on uranium or plutonium.
"Judging from the measurements, it probably falls short of being a hydrogen bomb although it (North Korea) claims it's a hydrogen bomb," Lee Cheol-woo, a member of the intelligence committee of the South Korean National Assembly, told reporters in Seoul.
The explosive yield was equivalent to six kilotons of TNT, nine times less than the atomic bomb the US dropped on Hiroshima in 1945.
US ambassador to the UN Samantha Power issued a statement following the Security Council’s two-hour closed-door meeting, calling for a tough response to Pyongyang "by imposing a tough, comprehensive and credible package of new sanctions."
She called on other world countries to exert "steadily increasing pressure" on the country, which has "isolated itself and impoverished its people through its reckless pursuit of weapons of mass destruction."
The Council also vowed in a statement that it will come up with a resolution against the alleged test.
Long-suspended negotiations with North Korea have so far failed to change the country’s nuclear program.
Last October, US and South Korean presidents urged the country to rejoin the six-nation talks in which China, Japan, and Russia would also partake.
Pyongyang’s move is considered by some as a means to gain the upper hand in future negotiations and gain credibility for North Korean leader Kim Jong-un.
Since he gained power in late 2011 from his father, Kim Jong-il, the young leader has tried to prove ambitious in regards to long-range missiles and nuclear weapons.
North Korea agency responded to the condemnations by vowing to continue to build up its nuclear program as deterrence against potential aggression from Washington.
North Korea's state news agency stressed in a statement that it will act as a responsible nuclear state, and will use its nuclear armament only to defend its sovereignty.