The test would mark the third time North Korea has detonated a nuclear device after previous tests were conducted in 2006 and 2009.
The declaration follows the UN Security Council’s condemnation of North Korea and expanded sanctions against the regime for launching a rocket in December.
“We absolutely refute all the illegal and outlawed resolutions adopted by the Security Council,” the commission said.
North Korea said the launch was a peaceful satellite mission, but the US and others say it was actually a test of long-range missile technology.
It has been reported that Pyongyang had finished technical preparations and could conduct an atomic test within days of a decision by leader Kim Jong-Un.
Satellite photos also appear to suggest North Korea had repaired rain damage at its nuclear test site and could conduct a detonation at two weeks’ notice.