Washington - President Barack Obama vowed on Friday to push for new international sanctions in retaliation for the "grave threat" posed by North Korea's latest nuclear test.
The US leader consulted by telephone with South Korean President Park Geun-Hye and Japanese Prime Minister Shinzo Abe following news of the reclusive country's fifth and most powerful test.
"We agreed to work with the UN Security Council, our other Six-Party partners, and the international community to vigorously implement existing measures imposed in previous resolutions, and to take additional significant steps, including new sanctions," Obama said in a statement.
"The United States condemns North Korea's September 9 nuclear test in the strongest possible terms as a grave threat to regional security and to international peace and stability," he said.
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Obama, who has pleaded since first taking office in 2009 for a world without nuclear weapons, denounced North Korea's actions as "unlawful and dangerous".
"To be clear, the United States does not, and never will, accept North Korea as a nuclear state," the president declared.
"As Commander in Chief, I have a responsibility to safeguard the American people and ensure that the United States is leading the international community in responding to this threat and North Korea's other provocations with commensurate resolve and condemnation," Obama said.
North Korea has been hit by five sets of UN sanctions since it first tested a nuclear device in 2006.
Obama reaffirmed, as he has done repeatedly following North Korean ballistic missile launches, the US commitment to "take necessary steps to defend our allies in the region," namely South Korea and Japan.
North Korea claimed on Friday it had successfully tested a nuclear warhead that could be mounted on a missile, drawing condemnation from South Korea's government over the "maniacal recklessness" of young ruler Kim Jong-Un.