Scientists and other governments suggested that North Korea's underground test on Monday was a partial failure, producing a smaller blast than planned.
A South Korean newspaper quoted a North Korean diplomat, whom it did not name, saying that the blast was "smaller in scale than expected".
"But the success in a small-scale (test) means a large-scale (test) is also possible," he said in comments posted on the Web site of the liberal newspaper Hankyoreh, which has good ties with the communist nation.
Philip Coyle, at the Center for Defense Information in Washington, a nongovernment think tank, expressed a growing view that "they got a partial result" and not the full-power explosion that they sought. Several Western estimates said the blast was less than a tenth the size of the bomb that the United States dropped on Hiroshima in 1945; the force of the Hiroshima bomb was equivalent to 15,000 tons of TNT.
But "for them it was enough ... to say that it was a success. It helps them to claim that they are a nuclear power, and that the world should take them seriously, which is what they want. But I wouldn't be surprised if after several months they don't try again."