SEOUL – North Korea on Tuesday staged its most powerful nuclear test yet, claiming a technological breakthrough with a “miniaturized” device in a striking act of defiance to global powers including its sole patron, China.
The isolated state said its third underground test, conducted in the face of severe warnings from the U.N. Security Council, was a direct riposte to what it termed U.S. “hostility.”
North Korea’s claim of miniaturization will be of particular concern, suggesting it is a step closer to fitting a nuclear warhead onto a ballistic missile.
The confirmation from state news agency KCNA came nearly three hours after seismic monitors detected a 4.9-magnitude earthquake in the area of the country’s Punggye-ri nuclear test site near the Chinese border.
Analysts said the timing appeared to be an attention-grabbing calculation from a state well versed in provocative acts, coming just ahead of U.S. President Barack Obama’s State of the Union address at the start of his second term.
Obama denounced the test and called for a “swift” and “credible” international response, as the Security Council readied to meet. Strong condemnation came from other regional powers, including Russia.
It was the North’s first nuclear test since new, youthful leader Kim Jong Un, took over from his father, Kim Jong Il. Analysts said it sent a bold message of intent following a successful long-range rocket launch in December.
“The launch and the test are empirical evidence that Kim and his regime have no intention of negotiating away the North’s nuclear program anytime soon,” said Paul Carroll, program director at the U.S.-based Ploughshares Fund.
North Korea’s two previous tests — in 2006 and 2009 — triggered waves of U.N. sanctions, and the Security Council was expected to debate new measures Tuesday morning in New York.
There was no immediate response from China, but a U.N. diplomat said Beijing had made its displeasure clear to Pyongyang.
“The Chinese gave the North Koreans a strong warning against carrying out a test as it became apparent that it was imminent,” the diplomat said, calling the test “a big challenge to the Chinese.”
On a technical level, along with miniaturization, experts are hungry to know if the North has switched from plutonium to a new, self-sustaining nuclear weaponization program using uranium.
The KCNA statement did not specify what fissile material was used, but noted that the test’s success had provided the North with a “diversified” nuclear deterrent.
The North has substantial deposits of uranium ore and it is much easier to secretly enrich uranium, which can be done in centrifuges rather than the nuclear reactor required for plutonium enrichment.
Tuesday’s explosion had a yield of 6 to 7 kilotons, South Korean Defense Ministry spokesman Kim Min Seok told reporters, significantly more than the 2006 and 2009 tests, which both used plutonium. The explosive yield was less than half the 15 kilotons of the world’s first atomic bomb dropped by the United States on the city of Hiroshima in 1945.
North Korea’s first test yielded less than 1 kiloton and was widely seen as a dud. The second test yielded between 2 and 6 kilotons, according to Seoul.
On top of uranium enrichment, a proven miniaturization ability will take on added significance following December’s rocket launch, which marked a major step forward in ballistic missile prowess, and provoked still-tighter U.N. sanctions.