South Korean Foreign Minister Ban Ki-Moon, due later on Monday to be effectively confirmed as next UN chief, said his government supports an emergency Security Council meeting following North Korea's nuclear test.
"My government fully supports the immediate convening of a Security Council meeting on Tuesday New York time," Ban said in a meeting with US ambassador Alexander Vershbow.
"We will very closely cooperate with the international community."
Ban's remarks came as the United States called for immediate action by the council after North Korea's announcement that it detonated its first nuclear device on Monday.
The Seoul government vowed to "sternly deal with" Pyongyang's act, saying it would not tolerate a nuclear-armed North Korea.
"Our government has issued a very strong statement expressing our deepest concern," Ban told the US envoy.
"All the consequences should be borne by North Koreans."
Ban said he had had emergency telephone conferences with his US and Japanese counterparts.
Ban, 62, is set to be designated as the next UN secretary general when the Security Council meets on Monday to formalize its choice.
It is expected to recommend him to the 192-member General Assembly, which will then formally elect him - most likely later in October.
Ban would take office in January 2006 to replace Kofi Annan, a Ghanaian who steps down after having completed two five-year terms.
Ban would be the first Asian to run the UN in more than 30 years.